Microwave applicator, plasma processing apparatus having same, and plasma processing method

ABSTRACT

In order to more accurately control the radiation characteristics of microwaves to improve the controllability of processing in radial and circumferential directions of an article, there are disclosed a microwave applicator and a plasma processing apparatus using the applicator, which comprise a circular waveguide having a surface provided with a plurality of slots for radiating microwaves, wherein the centers of the plurality of slots are offset in a direction parallel to the surface with respect to the center of the circular waveguide.

This application is a continuation-in-part of prior application Ser. No.09/426,744 filed Oct. 26, 1999, now abandoned, the contents of which areincorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a plasma processing apparatus forapplying plasma processing to an article to be processed (hereinafter,simply referred to as “article” as occasion demands) using microwaves,and more particularly to a microwave applicator having a circular (orannular) waveguide, a plasma processing apparatus provided therewith,and a plasma processing method.

2. Related Background Art

As plasma processing apparatuses that use microwaves as an excitationsource for plasma excitation, there have been known the plasmapolymerizing apparatus, the CVD apparatus, the surface modifyingapparatus, the etching apparatus, the ashing apparatus, and the cleaningapparatus and the like.

The CVD using such a so-called microwave plasma processing apparatus iscarried out, for example, as follows. A gas is introduced into a plasmageneration chamber and/or a film formation chamber of a microwave plasmaCVD apparatus, and a microwave energy is simultaneously applied togenerate a plasma in the plasma generation chamber to form ions orradicals through excitation, decomposition, ionization, or the like ofthe gas, thereby forming a deposited film on an article disposed in theplasma generation chamber or the film formation chamber apart from theplasma generation chamber. Further, a similar method can be used tocarry out plasma polymerization or surface modification such asoxidation, nitridation or fluorination of an organic substance.

Furthermore, the etching of an article using a so-called microwaveplasma etching apparatus is carried out, for example, as follows. Anetchant gas is introduced into a processing chamber of the apparatus,and a microwave energy is simultaneously applied to generate a plasma inthe processing chamber to thereby form ions, radicals or the likethrough excitation, decomposition, or ionization of the etchant gas,thereby etching a surface of an article disposed in the processingchamber with the thus formed ions, radicals or the like.

In addition, the ashing of an article using a so-called microwave plasmaashing apparatus is carried out, for example, as follows. An ashing gasis introduced into a processing chamber in the apparatus, and amicrowave energy is simultaneously applied to generate a plasma in theprocessing chamber to thereby form ions, radicals, ozone or the likethrough excitation, decomposition, or ionization of the ashing gas,thereby ashing a surface of an article, namely a photoresist disposed inthe processing chamber. As with the ashing, it is possible to effectcleaning for removing unwanted matter deposited on a to-be-processedsurface of an article.

In the microwave plasma processing apparatus, since microwaves are usedas a gas excitation source, electrons can be accelerated by an electricfield having a high frequency, thereby efficiently ionizing or excitinggas molecules. Thus, the microwave plasma processing apparatus isadvantageous in that the efficiency of ionization, excitation, anddecomposition of a gas is high, so that a high density plasma canrelatively easily be formed, and that it is possible to carry out fast,high quality processing at a low temperature. In addition, there is afurther advantage that the microwaves have a property of penetrating adielectric member such as quartz glass, so that the plasma processingapparatus can be constituted as a electrodeless discharge type, wherebyhighly clean plasma processing can be carried out.

To increase the processing speed of such a microwave plasma processingapparatus, plasma processing apparatuses utilizing electron cyclotronresonance (ECR) have been put to practical use. The ECR is a phenomenonin which when the magnetic flux density is 87.5 mT, the electroncyclotron frequency for electrons rotating around the magnetic line offorce is brought into conformity with the general frequency of themicrowaves of 2.45 GHz, whereby the electrons resonantly absorbmicrowaves to be accelerated, thereby generating a high density plasma.

Further, there have been proposed other types of plasma processingapparatuses for generating a high density plasma.

For example, U.S. Pat. No. 5,034,086 discloses a plasma processingapparatus using a radial line slot antenna (RLSA).

In addition, Japanese Patent Application Laid-Open No. 5-290995, U.S.Pat. No. 5,359,177, and EP 0564359 disclose plasma processingapparatuses using a circular waveguide with terminals.

Separately, as an example of a microwave plasma processing apparatus,there has recently been proposed an apparatus using an endless circularwaveguide in which a plurality of slots are formed on an inner sidesurface thereof as a device for uniform and efficient introduction ofmicrowaves (Japanese Patent Application Laid-Open No. 5-345982; U.S.Pat. No. 5,538,699).

However, when the conventional microwave plasma processing apparatusprovided with an endless circular waveguide having slots on an innerside surface thereof is used to effect processing in a high pressureregion at 100 mTorr (about 13.3 Pa) or more, as in the case of theashing processing, the diffusion of plasma is suppressed, so that theplasma may locally exist in the periphery of the chamber to reduce theprocessing speed for the center portion of the article. In addition, thevolume of the plasma generation space is required to be very large.

Further, Japanese Patent Application Laid-Open No. 7-90591 discloses aplasma processing apparatus using a disc-like microwave introducingdevice. In this apparatus, a gas is introduced into a waveguide andemitted to a plasma generation chamber through slots provided in thewaveguide.

Compared with these conventional apparatuses, the plasma processingapparatus previously proposed by the present inventors has aconfiguration as shown in FIG. 12.

In FIG. 12, reference numeral 1 designates a container (or vessel) whichcan be evacuated; 2 is a holding means for holding an article to beprocessed; 3 is a microwave supply means (also referred to as “microwaveapplicator”) comprising a circular hollow waveguide having a circularwaveguide therein; 4 is a dielectric window; and 7 is a gas supply pipehaving gas supply ports 7 a. In the apparatus configured using thesecomponents, microwaves are introduced into the microwave applicator 3through a microwave introducing port 15 and supplied from slots 3 bthrough the dielectric window 4 into the container 1.

FIGS. 13, 14 and 15 are schematic views illustrating the propagation ofmicrowaves through the circular waveguide of the microwave applicatorand the radiation of microwaves through the slots.

FIG. 13 shows the circular waveguide as seen from above with the slotsomitted, FIG. 14 shows a cross section taken along line 14—14, and FIG.15 shows a cross section taken along line 15—15.

The vicinity of the microwave introducing port 15 forms an equivalentcircuit of E-plane T-junction (or T-distribution), and microwavesintroduced through the microwave introducing port 15 have their coursechanged so as to fork clockwise d₂ and counterclockwise d₁. Each slot 3b is provided so as to intersect the microwave traveling directions d₁and d₂ so that the microwaves travel while being emitted through theslots.

Since the circular waveguide has no terminals and is endless, themicrowaves propagating in the directions d₁ and d₂ (z-axis direction)interfere mutually. Reference numeral C1 denotes an annulus (ring)formed by connecting width-wise centers of the waveguide, and thestanding waves of a predetermined mode can be generated more easily bysetting the length of this ring, that is, the circumferential length atan integral multiple of the guide wavelength (wavelength in waveguide).

FIG. 14 shows a cross section perpendicular to the microwave travelingdirection (z-axis direction). In this figure, the upper and bottomsurfaces 3 c of the waveguide form H-planes perpendicular to thedirection of electric field EF, while the right and left surfaces 3 d ofthe waveguide form E-planes parallel to the direction of the electricfield EF. Reference numeral C0 denotes the center of the longitudinaldirection of the slot 3 b, that is, the direction (x-axis direction)perpendicular to the microwave traveling/propagating direction.

Thus, the cross section of the waveguide that is perpendicular to themicrowave traveling direction has a rectangular shape having the x- andthe y-axes as the longer and the shorter sides, respectively.

Microwaves MW introduced into the circular waveguide 3 a are distributedby the distributor 10 of E-plane T-junction to the right and left of thedrawing and propagate at a guide wavelength longer than the wavelengthin the free space. The distributed microwaves interfere with each otherat their opposing portion to form standing waves at every ½ of the guidewavelength. Leakage waves EW radiated through the dielectric window 4from the slots 3 b provided at such positions as to maximize theelectric field crossing the slots generate a plasma P1 near the slots 3b. When the electron frequency of the generated plasma P1 exceeds thefrequency of the microwave power source (for example, when the electrondensity exceeds 7×10¹⁰ cm⁻³ at the power source frequency of 2.45 GHz),the so-called cut-off in which microwaves can not propagate through theplasma is caused, so that they propagate through the interface betweenthe dielectric window 4 and the plasma as surface waves SW. Surfacewaves SW introduced via adjacent slots interfere with each other to formantinodes (loops) of electric field at every ½ of the wavelength (λ∈_(r)^(−1/2) wherein λ is microwave wavelength in free space, and ∈_(r) isdielectric constant) of the surface waves SW. The antinodes of electricfield resulting from the interference of the surface waves leaked to theplasma generation space side generate a surface-wave interfered plasma(SIP) P2. At this time, when a processing gas is introduced into theplasma processing chamber, the processing gas is excited, decomposed, orionized by the thus generated high density plasma to enable processingof a surface of an article.

The use of such a microwave plasma processing apparatus can generate ahigh density, low potential plasma of a uniformity within ±3%, anelectron density 10¹²/cm³ or more, an electron temperature 3 eV or less,and a plasma potential 20 V or less in a space with an aperture of adiameter of 300 mm or more at a pressure of about 1.33 Pa and amicrowave power of 1 kW or more.

Thus, the gas can fully be reacted and supplied in an active state to asurface to be processed. Furthermore, when the pressure is 2.7 Pa andthe microwave power is 2 kW, any current due to the microwaves cannot bedetected at a location apart by 8-10 mm away from the inner surface ofthe dielectric window. This means that a very thin plasma layer isformed near the dielectric window in a high pressure region where plasmadiffusion is suppressed. Thus, article surface damage due to incidentions can be reduced, thereby enabling high quality and high speedprocessing even at low temperatures.

Incidentally, the circumferential length of the circular waveguide mustbe selected from 2 times, 3 times, 4 times, . . . the guide wavelength(i.e., integral multiple of the guide wavelength) depending theprocessing area of an article. When air exists at atmospheric pressurein the waveguide, considering that the guide wavelength is about 159 mm,selectable circumferential length is about 318 mm, about 477 mm, about636 mm, . . . Converting these values to the diameter of the ringprovides about 101 mm, about 151 mm, about 202 mm.

On the other hand, when an ordinary 8-inch or 12-inch wafer is used asan article to be processed, the diameters thereof are about 200 mm andabout 300 mm, respectively. Even when an optimum combination of the bothmembers, it can not be said that uniformity of plasma and uniformity ofprocessing are attained sufficiently. For example, there is caused aphenomenon in which the plasma density is lowered near the center of thering or near the center of the article, so that the processing speed isdecreased.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a microwave applicatorthat can more accurately control the microwave radiation characteristicsin radial direction of the ring or a direction equivalent thereto.

Another object of the present invention is to provide a plasmaprocessing apparatus and method that can more efficiently improve theuniformity of processing in a radial direction of an article.

Still another object of the present invention is to provide a microwaveapplicator that can improve the microwave radiation uniformity in radialand circumferential directions of the ring or a direction equivalentthereto.

Yet another object of the present invention is to provide a plasmaprocessing apparatus and method that can wholly improve the uniformityof processing in radial and circumferential directions or a directionequivalent thereto of an article.

According to an aspect of the present invention, there is provided amicrowave applicator or a plasma processing apparatus comprising acircular waveguide having a surface provided with a plurality of slotsfor radiating microwaves, wherein the centers of the plurality of slotsare offset in a direction parallel to the surface with respect to thecenter of the circular waveguide.

According to another aspect of the present invention, there is provideda microwave applicator or a plasma processing apparatus comprising acircular waveguide having a flat surface provided with a plurality ofslots for radiating microwaves, wherein the plurality of slots arediscontinuous linear slots provided in a direction intersecting themicrowave travelling direction.

According to still another aspect of the present invention, there isprovided a plasma processing apparatus comprising a container, a gassupply port for supplying a processing gas into the container, and amicrowave applicator for supplying microwaves into the container througha dielectric window, the microwave applicator comprising an endlesscircular waveguide having a plurality of slots provided at apredetermined interval in a plane thereof in contact with the dielectricwindow, wherein the centers of the slots are on a circle having a radiusr_(c) approximately represented byr _(c) =n ₁λ_(s)/{2 tan(π/(2n _(g)))}{1+cos(π/n _(g))}wherein n₁, is the number of antinodes of surface standing wavesgenerated between the slots, λ_(s). is the wavelength of surface waves,n_(g) is the ratio of the circumferential length l_(g) of the circularwaveguide to the guide wavelength λ_(g).

According to yet another aspect of the present invention, there isprovided a plasma processing method comprising the steps of placing anarticle in a container with a microwave transmissive dielectric window;evacuating the container; introducing a processing gas into thecontainer; and supplying microwaves into the container through anendless circular waveguide having a plurality of slots provided byperforation at a predetermined interval in a plane thereof in contactwith the dielectric window and configured such that the centers of theslots are on a circle having a radius r_(c) approximately represented byr _(c) =n ₁λ_(s)/{2 tan(π/(2n _(g)))}{1+cos(π/n _(g))}wherein n₁ is the number of antinodes of surface standing wavesgenerated between the slots, λ_(s) is the wavelength of surface waves,n_(g) is the ratio of the circumferential length l_(g) of the circularwaveguide to the guide wavelength λ_(g), thereby generating a plasma inthe container.

According to still a further aspect of the present invention, there isprovided a plasma processing apparatus comprising an internallyevacuatable container and a gas supply port for supplying a processinggas into the container, for plasma processing an article arranged in thecontainer, further comprising means for supplying a microwave energy forgenerating a plasma of the gas in the container, the means comprising anendless circular waveguide having a plurality of slots provided at apredetermined interval in a plane on the dielectric window side thereof,wherein the centers of the plurality of slots are offset in a directionparallel to the plane with respect to the center of the circularwaveguide such that the centers of the slots are on a circle having aradius r_(c) approximately represented byr _(c) =n ₁λ_(s)/{2 tan(π/(2n _(g)))}{1+cos(π/n _(g))}wherein n₁ is the number of antinodes of surface standing wavesgenerated between the slots, λ_(s) is the wavelength of surface waves,n_(g) is the ratio of the circumferential length l_(g)of the circularwaveguide to the guide wavelength λ_(g).

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view of a plasma processing apparatus according tothe present invention;

FIG. 2 is a plan view showing an example of a slotted flat plate used inthe present invention;

FIG. 3 is a schematic sectional view of another plasma processingapparatus according to the present invention;

FIG. 4 is a plan view showing another example of a slotted flat plateused in the present invention;

FIG. 5 is a schematic sectional view of a microwave plasma processingapparatus using a circular waveguide according to the present invention;

FIG. 6 is a plan view of a slotted flat plate;

FIG. 7 is a schematic sectional view of a microwave plasma processingapparatus using a tangential introduction type circular waveguideaccording to the present invention;

FIG. 8 is a schematic sectional view of another microwave plasmaprocessing apparatus according to the present invention;

FIG. 9 is a schematic sectional view of still another microwave plasmaprocessing apparatus according to the present invention;

FIGS. 10A, 10B, 10C, 10D, and 10E are schematic views showing an exampleof a plasma processing method;

FIGS. 11A, 11B, and 11C are schematic views showing another example of aplasma processing method;

FIG. 12 is a schematic view showing the configuration of a plasmaprocessing apparatus;

FIG. 13 is a schematic sectional view of a microwave applicator;

FIG. 14 is a schematic sectional view of a waveguide;

FIG. 15 is a schematic sectional view illustrating radiation ofmicrowaves;

FIG. 16A is a schematic sectional view showing a plasma processingapparatus according to another embodiment of the present invention, FIG.16B is a schematic view of a microwave applicator used in the presentinvention, and FIG. 16C is a schematic view showing the state ofmicrowave propagation in a microwave applicator used in the presentinvention;

FIG. 17 is a schematic view showing a configuration of slots;

FIG. 18 is a schematic view of a microwave applicator used in thepresent invention;

FIG. 19 is a schematic view of another microwave applicator used in thepresent invention; and

FIG. 20 is a schematic view of another microwave applicator used in thepresent invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

(Embodiment 1)

FIG. 1 is a schematic sectional view showing a plasma processingapparatus according to a preferred embodiment of the present invention.

The microwave applicator 3 comprising a circular waveguide 13 having asurface provided with a plurality of slots 33 for radiating microwavesis characterized in that the centers C2 of the plurality of slots 33 areoffset in a direction parallel to the surface with respect to the centerC1 of the circular waveguide 13.

Specifically, reference numeral 1 designates a vacuum container whichcan house the article to be processed W therein and generate a plasma inthe plasma generation chamber 9 and is, for example, a container of anatmosphere-open-type or a container isolated from the atmosphere by aload lock chamber provided adjacent thereto (not shown).

Reference numeral 2 denotes an article holding means called “susceptor”or “holder” for housing the article W in the vacuum container 1 andholding the article, which has lift pins 12 that can elevate and lowerthe article W and which may further be provided with a temperaturecontrolling means such as a heater for heating the article W or a coolerfor cooling the article W as the occasion demands.

Reference numeral 3 indicates a microwave applicator for supplyingmicrowave energy to generate a plasma in the vacuum container 1 in whichthe slots 33 are offset inside. Incidentally, the slots shown in FIG. 14are not offset.

Reference numeral 4 designates a dielectric window that seals the insideof the vacuum container 1 airtight while allowing microwaves to passtherethrough.

Reference numeral 5 denotes a microwave waveguide, and reference numeral6 denotes a microwave power source.

Reference numeral 7 designates a gas supply passage for supplying aprocessing gas to be converted into a plasma by microwaves, whichobliquely extends upward and has a gas supply port 17 at the endthereof.

The gas supply passage 7 communicates with a gas supply system 27consisting of gas cylinders 57, valves 47, flow rate controllers 37 andthe like.

Reference numeral 8 denotes an exhaust passage for exhausting the insideof the container 1, which communicates via an exhaust opening (notshown) with an exhaust system including a vacuum pump 18, a valve 28, orthe like.

FIG. 2 is a plan view showing an example of the slotted flat plate 23used in the microwave applicator 3 of the apparatus of FIG. 1.

The slotted flat plate 23 has the plurality of slots 33. The pluralityof slots 33 are offset in a direction parallel to the surface of theflat plate 23 such that the line formed by connecting the centers C2 ofthe slots 33 together is positioned inside in the radial direction ofthe line formed by connecting the width-wise centers C1 of the circularwaveguide 13 together. In the figure, C3 indicates the position of theouter side surface of the circular waveguide 13 and C4 indicates theinner side surface thereof.

A plasma processing method using the apparatus shown in FIG. 1 isdescribed below.

A processing gas is supplied from the gas supply port 17 to the insideof the vacuum container 1, which has been pressure-reduced and exhaustedto a predetermined pressure.

The processing gas is emitted to the space 9 which forms a plasmageneration chamber and then flows to the exhaust passage 8.

On the other hand, microwaves generated in the microwave power source 6such as a magnetron are propagated via a waveguide 5 such as a coaxial,cylindrical, or rectangular waveguide and are introduced via theintroducing port 15 into the microwave applicator 3.

Microwaves introduced through an upper H-plane opposing one slot 33 areemitted through the slot while propagating through the endless circularwaveguide 13 of the microwave applicator 3 clockwise andcounterclockwise in the view of FIG. 2.

Since longitudinal slots 33 crossing the propagating/traveling directionof the microwaves propagating and travelling in, e.g., TE₁₀ mode throughthe waveguide are provided in an H-plane of the circular waveguide 13,the microwaves are radiated to the space 9 through the slots 33.

The microwaves are supplied to the space 9 through a microwavetransmissive window 4 made of a dielectric.

The processing gas present in the space 9 is excited by the microwaveenergy to generate a plasma P. The mechanism of the microwave radiationand plasma generation is as described with reference to FIG. 15.

The surface of the article W is subjected to a surface treatment usingthis plasma. The plasma P may be present only under the slots as shownin FIG. 1 or may spread over the entire bottom surface of the dielectricwindow 4, depending on the power of supplied microwaves and the pressureinside the container.

In contrast to the above mentioned positioning of the slots, the slotsmay be offset outside depending the size of the article W or thecircumferential length of the waveguide of the microwave applicator.

(Embodiment 2)

According to another preferred embodiment of the present invention,there is provided a microwave applicator comprising a circular waveguidehaving a flat surface provided with a plurality of slots for radiatingmicrowaves, characterized in that the plurality of slots arediscontinuous linear slots 33, 34 provided in a direction intersectingthe microwave travelling direction.

FIG. 3 is a schematic sectional view showing such a plasma processingapparatus.

The apparatus has a slotted flat plate 23 as shown in FIG. 4. Theapparatus is different from the apparatus of FIG. 1 in provision of theslotted flat plate 23 as shown in FIG. 4 and an article biassing powersource 22.

The apparatus is configured such that the pressure inside of the space 9can be reduced to control the plasma to broaden, and that plasmaprocessing can be carried out while applying a bias voltage to thearticle from the bias power source 22. This configuration is suitablefor etching processing.

Further, it is preferred that the holding means 2 is provided with acooler to suppress the temperature rise of the article W as the occasiondemands.

The same reference numerals as used in FIGS. 1 and 2 denote the samemembers as those in the apparatus of the embodiment of FIG. 1 and thedescription thereof is omitted.

FIG. 4 is a plan view showing another example of the slotted flat plateof the microwave applicator used in the present invention.

The slotted flat plate of FIG. 4 is different from that of FIG. 2 infurther provision of a plurality of slots 43 on extension lines of theslots 33.

The outer slots 43 are also offset such that the line formed byconnecting the centers C5 of the slots 43 together is positioned outsidein the radial direction of the line formed by connecting the width-wisecenters C1 of the circular waveguide 13 together.

Each pair of the slots 33 and 43 provided in the same radial directionis linearly discontinuous, so that radial radiation of microwaves can becarried out more uniformly than the conventional slots. Further, ascompared with the case where a pair of the slots 33 and 43 areintegrated into a single long-size slit, circumferential radiation(i.e., radiation in the microwave travelling direction) can be performedmore uniformly.

The offset amount of the slots used in the present invention is suitablydetermined depending on the processing conditions used. Especially, whenthe slotted flat plate 23 is so configured as to be interchangeable withregard to the conductive base member with a recess for forming thewaveguide 13, it is possible to flexibly attend to a change inprocessing conditions.

The shape of the heterocentral slot used in the present invention inwhich the center of the slot is different from the center of thecircular waveguide may be a single rectangle perforation, or mayalternatively be a combination of plural perforations having a length of¼ to ⅜ of the guide wavelength and arranged discontinuously along aline, as long as the center of each slot is offset inside or outsidewith regard to the center line of the waveguide.

(Embodiment 3)

With reference to FIGS. 5 and 6, an endless circular waveguide accordingto another preferred embodiment of the present invention and a microwaveplasma processing apparatus using the same are described.

FIG. 5 is a schematic longitudinal sectional view of a microwave plasmaprocessing apparatus using a circular waveguide having a flat plate withdiscontinuous linear slots as a example of the present invention, andFIG. 6 is a plan view of the slotted plate of the circular waveguide ofFIG. 5.

The apparatus is different from the apparatus shown in FIGS. 3 and 4 inthat the size of the circular waveguide (microwave applicator) 3 islarger than that of the article W, that the gas supply port 17 isprovided downward, and that there are eight pairs of discontinuouslinear slots 33, 43 as offset inside and outside, respectively. Further,the holding means 2 is provided with a heater 114 for temperaturecontrol of the article W.

The exhaust system and gas supply system may be the same as shown inFIGS. 1 and 3.

In FIG. 5, the slots 33 and 43 are not depicted for convenience sake.

The generation of a plasma and the processing are carried out asfollows. The inside of the container 1 is evacuated via an exhaustsystem (not shown). Subsequently, a plasma processing gas is introducedat a predetermined flow rate into the container 1 via the gas supplypassage 7. Then, a conductance valve (not shown) provided in the exhaustsystem (not shown) is adjusted to maintain the inside of the container 1at a predetermined pressure. A desired power from a microwave powersource (not shown) is introduced into the container 1 through themicrowave applicator 3 to generate a plasma in the container 1. At thistime, the introduced processing gas is excited, decomposed, or ionizedby the high density plasma as generated to process the surface of thearticle W put on the holding means 102.

As the material of the circular waveguide which forms the microwaveapplicator used in the microwave plasma processing apparatus accordingto the present invention, any conductor may be used, but an optimalmaterial is stainless steel plated with Al, Cu, or Ag/Cu that has a highconductivity in order to minimize the propagation loss of microwaves.

The direction of the microwave introducing port 15 of the circularwaveguide used in the present invention may be perpendicular to theH-plane as shown in the figures so that microwaves are distributed atthe introducing section to the right and left directions relative to themicrowave propagation space or may be parallel to the H-plane andtangential relative to the propagation space, as long as it canefficiently introduce microwaves into the waveguide in the microwaveapplicator.

The slot interval in the microwave travelling direction of the microwaveapplicator used in the present invention is optimally ½ of the guidewavelength. In the present invention, the length of each of thecontinuous portions of the discontinuous slot, i.e., the lengths of theslots 33 and 43 are each preferably within the range of ¼ to ⅜ of theguide wavelength.

The discontinuous linear slot 33, 43 is in a direction which intersectsthe microwave travelling direction 121. That is, the longitudinaldirection of the slot intersects the microwave travelling direction 121,for example, perpendicularly in this embodiment. In this embodiment,since a rectangular waveguide is shaped like a ring (not limited to acircular ring but including an ellipsoidal, square, pentagonal ring, orthe like) to be circular, and since microwaves of TE₁₀ mode (H₀₁ mode)are allowed to propagate therein, one discontinuous linear slot (onepair of slots) corresponds to one loop of the oscillation. In thefigure, reference numeral 120 schematically show the magnetic field.

A material suitable for the dielectric window 4 is anhydrous syntheticquartz, and the window has a diameter 299 mm and a thickness 12 mm. Thecircular waveguide 3 having the flat plate with discontinuous linearslots (hereinafter, simply referred to as “flat plate type circularwaveguide) has a 27 mm×96 mm inner wall cross section and a centraldiameter of 202 mm. As the material of the flat plate type circularwaveguide 3, Al is used entirely in order to suppress the propagationloss of microwaves. In the H-plane of the circular waveguide 3, areformed eight pairs of the discontinuous linear slots 33, 43. Inside andoutside of the center line of the waveguide, is arranged each pair ofrectangular slots of 42 mm in length and 3 mm in width linearly, and therespective pairs of slots are formed radially at an interval of ½ of theguide wavelength. Although the guide wavelength depends on the frequencyof microwaves used and the size of the cross section of the waveguide,the use of microwaves of a frequency 2.45 GHz and a waveguide of theabove mentioned size provides a guide wavelength of about 159 mm. In thecircular waveguide 103 used, there are formed rectangular slots of 42 mmin length and 3 mm in width in the total number of sixteen (16) insideand outside the center line of the waveguide at an interval of 45°. Tothe circular waveguide 3, are connected a 4E tuner, a directionalcoupler, an isolator, and a microwave power source (not shown) offrequency 2.45 GHz in this order.

The microwave plasma processing apparatus shown in FIGS. 5 and 6 wasused to generate a plasma under the conditions of an Ar flow rate of 500sccm, pressures of 1.33 Pa and 133 Pa, and a microwave power of 3.0 kW,and the plasma obtained was measured. The plasma was measured as followsusing a single probe method. The voltage applied to the probe was variedwithin a range of −50 V to +100 V, and a current flowing through theprobe was measured by an I-V measuring device. The electron density, theelectron temperature and the plasma potential were calculated from thethus obtained I-V curve by the Langmuir method. As a result, theelectron density was 2.1×10¹²/cm³±2.7% (within φ 300 plane) at 1.33 Paand 9.6×10¹¹/cm³±5.4% (within φ 300 plane) at 133 Pa, and it wasconfirmed that a high density, uniform plasma was formed even in a highpressure region. The expression “within φ 300 plane” means the inside ofa circle of 300 mm in diameter.

[Embodiment 4]

FIG. 7 is a schematic longitudinal sectional view of a microwave plasmaprocessing apparatus using a tangential introduction type circularwaveguide of the flat plate type.

The generation of plasma and processing is the same as in the previouslydescribed embodiments.

A desired power from a microwave power source (not shown) is introducedinto a flat plate type circular waveguide 3 through an introducing port15 formed in the E-plane. The introduced microwaves are supplied to theinside of the plasma generation space 9 through the dielectric window 4via slots formed at an interval of ½ of the guide wavelength. Microwavesthat have propagated through the waveguide 3 one round without beingintroduced to the space 9 interfere with newly introduced microwavesnear the introducing portion 15 to strengthen each other, and most ofthe microwaves are introduced to the inside of the plasma generationspace 9 before they have propagated through the waveguide severalrounds. In the figure, the configuration of the other portion than themicrowave introducing port 15 is the same as Embodiment 3. Further, FIG.7 is depicted with the slots omitted for convenience sake.

The microwave plasma processing apparatus shown in FIG. 7 was used togenerate a plasma under the conditions of an Ar flow rate of 500 sccm,pressures of 1.33 Pa and 133 Pa, and a microwave power of 3.0 kW, andthe plasma obtained was measured. The plasma was measured as followsusing a single probe method. The voltage applied to the probe was variedwithin a range of −50 V to +100 V, and a current flowing through theprobe was measured by an I-V measuring device. The electron density, theelectron temperature and the plasma potential were calculated from thethus obtained I-V curve by the Langmuir method. As a result, theelectron density was 1.9×10¹²/cm³±2.7% (within φ 300 plane) at 1.33 Paand 8.7×10¹¹/cm³±5.6% (within φ 300 plane) at 133 Pa, and it wasconfirmed that a high density, uniform plasma was formed even in a highpressure region.

(Embodiment 5)

FIG. 8 is a schematic longitudinal sectional view of a microwave plasmaprocessing apparatus using an RF bias application mechanism. In thefigure, reference numeral 22 denotes an RF bias application means. FIG.8 is also depicted with the slots omitted for convenience sake.

The generation of a plasma and the processing are carried out asfollows. The article W is put on the holding means 2 and is heated to adesired temperature using the heater 114. The plasma generation space 9is evacuated via an exhaust system (not shown). Subsequently, a plasmaprocessing gas is introduced at a predetermined flow rate into theplasma generation space 9. Then, a conductance valve (not shown)provided in the exhaust system (not shown) is adjusted to maintain theplasma generation space 9 at a predetermined pressure. The RF biasapplication means 22 is used to supply an RF power to the holding means22, while a desired power from a microwave power source (not shown) isintroduced into the plasma generation space 9 through the dielectricwindow 4 via the flat plate type circular waveguide 3. The electricfield of the introduced microwaves accelerates electrons to generate aplasma in the plasma generation space 9. At this time, the processinggas is excited, decomposed or ionized by the high density plasmagenerated to process the surface of the article W. In addition, the RFbias can be used to control the kinetic energy of ions incident upon thearticle.

(Embodiment 6)

FIG. 9 is a schematic longitudinal sectional view of a microwave plasmaprocessing apparatus having a cooling mechanism for temperature control.In the figure, reference numeral 414 denotes a cooler for cooling thearticle. FIG. 9 is also depicted with the slots omitted for conveniencesake.

The generation of a plasma and the processing are carried out asfollows. The article W is put on the holding means 102 and is cooledusing the cooler 414. The plasma generation space 9 is evacuated via anexhaust system (not shown). Subsequently, a plasma processing gas isintroduced. Then, a conductance valve (not shown) provided in theexhaust system (not shown) is adjusted to maintain the inside of theplasma generation space 9 at a predetermined pressure. The RF biasapplication means 302 is used to supply an RF power to the holding means2, while a desired power from a microwave power source (not shown) isintroduced into the plasma generation space 9 through the dielectricwindow 4 via the flat plate type circular waveguide 3. The electricfield of the microwaves introduced accelerates electrons to generate aplasma. Using the cooler 414 can suppress the overheating of the articlecaused by ion incidence when a high density plasma and a high bias areused.

(Embodiment 7)

A seventh embodiment of the present invention will be described below.

FIGS. 16A to 16C are schematic views showing a microwave plasmaprocessing apparatus. Specifically, FIG. 16A is a schematic sectionalview of the apparatus; FIG. 16B is a schematic plan view of a microwaveapplicator of the apparatus; and FIG. 16C is a schematic view showingthe state of microwave propagation in the microwave applicator.

In the figures, reference numeral 1 designates a container that definesa plasma processing chamber 9 therein; W is an article to be processed;2 is a supporting means for holding the article; 114 is a means foradjusting the temperature of the article W; 22 is a high frequency biasapplying means; 7 is a processing gas supply port; 18 is an exhaustmeans such as an exhaust pump; 28 is an exhaust conductance adjustingmeans; 4 is a dielectric window for isolating the plasma processingchamber 9 from the atmosphere; 3 is a microwave applicator comprised ofan endless circular waveguide with slots for introducing microwaves intothe plasma processing chamber 9 through the dielectric window 4; 13 is amicrowave waveguide in the endless circular waveguide; 15 is a microwaveintroducing port that forms an E-junction for distributing themicrowaves introduced in the endless circular waveguide into the rightand the left; STW is standing waves generated by interference ofmicrowaves distributed by the E-junction and propagating in thewaveguide; and 33 is a plurality of slots provided by perforating aplane (here H-plane) in contact with the dielectric window 4 at apredetermined interval.

Further, reference numeral SW designates surface waves introducedthrough the slots 33 and propagating in the surface of the dielectricwindow 4, and SSTW denotes surface standing waves generated byinterference of the surface waves SW emitted from the adjoining slots33. Since a plasma is generated on the lower side of the dielectricwindow 4 by electronic excitation with the surface standing waves SSTW,the plasma is called a surface-wave interfered plasma.

In the present embodiment, the slots 33 are not located on the centerline of the microwave waveguide 13 of the endless circular waveguide,but are located such that the centers of slots 33 are on a circle C2having a radius r_(c) approximately represented byr _(c) =n ₁λ_(s)/{2 tan(π/(2n _(g)))}{1+cos(π/n _(g))}wherein n₁. is the number of antinodes of surface standing waves SSTWgenerated between slots 33, λ_(s) is the wavelength of the surface wavesSW, n_(g) is the multiplicative number of the circumferential lengthl_(g) of the circular waveguide 13 with regard to the guide wavelengthλ_(g) (i.e., the ratio l_(g)/λ_(g)).

The reason for the above will be described below with reference to FIG.17.

In a case where it can be approximated that an odd number of surfacestanding waves SSTW are generated in plurality in a direction parallelto the direction of arrangement of the slots between slots 33 byinterference of the surface waves SW generated from adjoining slots 33,the surface standing waves SSTW are generated at an interval of ½ of thewavelength λ_(s) of the surface waves SW. Therefore, in order to mostefficiently generate the surface standing waves SSTW equidistant fromeach other, the propagation length of the surface waves SW between slots(which is the same as the distance L between central standing waves)needs to be set as follows.

 L=n ₁λ_(s)/2

In a general case where it can not be approximated that the direction ofarrangement of the slots and the direction of arrangement of the surfacestanding waves SSTW generated in plurality are parallel to each other,the propagation length L needs to be alternatively set as follows.L=n ₁λ_(s)/{1+cos(π/n _(g))}

Further, the propagation length L is also represented using the radiusr_(c) of the circle on which the centers of the slots should exist and ahalf angle θ of the angular spacing π/n_(g) of the slots as follows.L=2r _(c) tan θ=2r _(c) tan(π/2n _(g))Accordingly, the radius r_(c) of the circle on which the centers of theslots should exist (hereinafter, simply referred to as “slot centerradius r_(c)”) is represented as follows.r _(c) =n ₁λ_(s)/{2 tan(π/(2n _(g)))}{1+cos(π/n _(g))}

In this case, it is preferred that the value of n_(g) (=l_(g/λ) _(g)) iswithin the range of 2 to 5. Further, it is preferred that the number n₁of antinodes of the surface standing waves SSTW generated between slots33 (hereinafter, simply referred to as “interslot surface standing waveantinode number n₁”) is any one of 3, 5 or 7.

For example, the slot center radii r_(c) when the interslot surfacestanding wave antinode number n₁ is 3 or 5, the microwave frequency is2.45 GHz (λ_(o): 22.44 mm), n_(g) is 2, 3 or 4, and the material of thedielectric window is quartz glass (dielectric constant ∈_(w): 3.8) oraluminium nitride (dielectric constant ∈_(w): 9.8) are shown in TABLE 1.

TABLE 1 Dielectric (ε_(w)) n₁ n_(g) = 2 n_(g) = 3 n_(g) = 4 quartz 378.6 mm 103.9 mm 129.2 mm glass (3.8) aluminium 3 58.7 mm  67.7 mm  82.9mm nitride (9.8) aluminium 5 76.6 mm 101.9 mm 127.2 mm nitride (9.8)

The generation of a plasma and the processing using the microwave plasmaprocessing apparatus are carried out as follows.

First, the plasma processing chamber 9 is evacuated via the exhaustmeans 18. Subsequently, a plasma processing gas is introduced at apredetermined flow rate into the plasma processing chamber 9 via theprocessing gas supply port 7.

Then, the conductance adjusting means 28 provided between the plasmaprocessing chamber 9 and the exhaust means 18 is adjusted to maintainthe plasma processing chamber 9 at a predetermined pressure. Ifnecessary, a bias voltage is applied to the article W with the highfrequency bias applying means 22. A desired power from a microwave powersource MW is supplied into the plasma processing chamber 9 through theendless circular waveguide 13.

At this time, microwaves of TE₁₀ mode introduced into the endlesscircular waveguide 13 are distributed into two of the right and left atthe E-junction of the introducing port 15 and propagate within thewaveguide 13 at a guide wavelength longer than the wavelength in thefree space. The distributed microwaves interfere with each other togenerate standing waves STW having an “antinode” at every ½ of the guidewavelength. Microwaves introduced into the plasma processing chamber 9through the dielectric window 4 from the slots 33 provided at suchpositions as to maximize the current flowing the conductive plane(H-plane in this case) of the waveguide 13, i.e., at the centers betweenadjoining two antinodes generate a plasma in the vicinity of the slots33.

When the electron plasma frequency of the generated plasma exceeds thepower source frequency (for example, when the electron plasma frequencyexceeds the power source frequency of 2.45 GHz in the case where theelectron density exceeds 7×10¹⁰ cm⁻³), the so-called cut-off in whichmicrowaves can not propagate through the plasma is caused. Further, whenthe electron density increases and the skin depth δ defined byδ=(2/ωμ_(o)σ)^(1/2)(wherein, ω is the angular frequency of a power source, μ_(o) is thespace permeability, and σ is the plasma conductivity) becomessufficiently small (for example, when the electron density becomes2×10¹² cm⁻³ or more), the skin depth becomes 4 mm or less, themicrowaves propagate as the surface waves SW in the surface of thedielectric window 4.

Surface waves SW introduced via adjoining slots 33 interfere with eachother to generate surface standing waves SSTW at every half of thewavelength of surface waves SW approximately represented byλ_(s)=λ_(o)∈_(r) ^(−1/2)wherein, λ_(o) is the free-space microwave wavelength, and ∈_(r) is thedielectric constant of the dielectric.

The surface standing waves SSTW leaked to the plasma processing chamber9 accelerate electrons, thus generating a surface-wave interfered plasma(SIP). At this time, when a processing gas is introduced through theprocessing gas supply port 7 into the plasma processing chamber 9, theprocessing gas is excited by the thus generated high density plasma toprocess a surface of the article W placed on the support means 2. Theshape of the slots 33 provided in the microwave plasma processingapparatus in accordance with the present embodiment need not necessarilybe a rectangle perforation with a length of ¼ to ⅜ of the guidewavelength as long as the centers of the slots 33 are on the circle C2having a radius r_(c) approximately represented byr _(c) =n ₁λ_(s)/{2 tan(π/(2n _(g)))}{1+cos(π/n _(g))}.(Embodiment 8)

A microwave applicator of the microwave plasma processing apparatus inaccordance with an eighth embodiment of the present invention will bedescribed with reference to FIG. 18 in which n_(g) is 3, the interslotsurface standing wave antinode number n¹ is 3, and the material of thedielectric window is quartz glass (dielectric constant ∈_(w): 3.8). Theconfiguration of the apparatus body is similar to that shown in FIGS.16A to 16C.

In the present embodiment, the slots 33 are formed such that the centersof the slots are on a circle C5 with a radius r_(c) of about 103.9 mmoutside the center line of the microwave waveguide 13 of the endlesscircular waveguide. The radius r_(c) of the circle C5 satisfies theabove mentioned equality.

With the apparatus of the above mentioned configuration, microwaves ofTE₁₀ mode introduced into the endless circular waveguide 13 aredistributed into two of the right and left at the E-junction andpropagate within the waveguide 13 at a guide wavelength longer than thewavelength in the free space. The distributed microwaves interfere witheach other to generate standing waves STW having six “antinodes” atevery ½ of the guide wavelength. Microwaves introduced into the plasmaprocessing chamber 9 through the dielectric window 4 from the slots 33provided at such positions as to maximize the current, i.e., at thecenters between adjoining two antinodes generate a plasma in thevicinity of the slots 33.

When the electron plasma frequency of the generated plasma exceeds thepower source frequency (for example, when the electron plasma frequencyexceeds the power source frequency of 2.45 GHz in the case where theelectron density exceeds 7×10¹⁰ cm⁻³), the so-called cut-off in whichmicrowaves can not propagate through the plasma is caused. Further, whenthe electron density increases and the skin depth δ defined byδ=(2/ωμ_(o)σ)^(1/2)(wherein, ω is the angular frequency of a power source, μ_(o) is thespace permeability, and σ is the plasma conductivity) becomessufficiently small (for example, when the electron density becomes2×10¹² cm⁻³ or more, the skin depth becomes 4 mm or less), themicrowaves propagate as the surface waves SW in the surface of thedielectric window 4 made of the quartz glass.

Surface waves SW introduced via adjoining slots 33 interfere with eachother to generate surface standing waves SSTW at about every 31 mm(i.e., at an interval of about 31 mm).

The surface standing waves SSTW leaked to the plasma processing chamberaccelerate electrons, thus generating a surface-wave interfered plasmaSIP.

The material of the dielectric window is anhydrous synthetic quartz, andthe window has a diameter 300 mm and a thickness 12 mm. The endlesscircular waveguide has a 27 mm×96 mm inner wall cross section and acentral diameter of 152 mm (the circumferential length l_(g) of thewaveguide being three times the guide wavelength λ_(g)).

As the material of the endless circular waveguide 3, Al is used entirelyin order to suppress the propagation loss of microwaves. In the H-planeof the endless circular waveguide 3, are formed slots 33 for introducingmicrowaves into the plasma processing chamber 9. The slots 33 each havea rectangular shape of 40 mm in length and 4 mm in width, and are formedradially at an interval of 60° in the total number of six (6) with thecenters of the slots being on the circle C5 of the radius of 103.9 mm.To the endless circular waveguide, are connected a 4E tuner, adirectional coupler, an isolator, and a microwave power source (notshown) of frequency 2.45 GHz in this order.

The microwave plasma processing apparatus with the microwave applicatorshown in FIG. 18 was used to generate a plasma under the conditions ofan Ar flow rate of 500 sccm, a pressure of 1.33 Pa, and a microwavepower of 3.0 kW, and the plasma obtained was measured. The plasma wasmeasured as follows using a single probe method. The voltage applied tothe probe was varied within the range of −50 V to +100 V, and a currentflowing through the probe was measured by an I-V measuring device, andthe electron density, the electron temperature and the plasma potentialwere calculated from the thus obtained I-V curve by the Langmuir method.As a result, the electron density was 2.1×10¹²/cm³±2.7% (within φ 300plane) at 1.33 Pa, and it was confirmed that a high electron density,stable plasma was formed even in a low pressure region.

(Embodiment 9)

A microwave applicator of the microwave plasma processing apparatus inaccordance with a ninth embodiment of the present invention will bedescribed with reference to FIG. 19 in which the (waveguidecircumferential length)/(guide wavelength) ratio n_(g) is 3, theinterslot surface standing wave antinode number n₁ is 3, and thematerial of the dielectric window is aluminium nitride (dielectricconstant ∈_(w): 9.8). The configuration of the apparatus body is similarto that shown in FIGS. 16A to 16C.

In the present embodiment, the slots 33 are formed offset such that thecenters of slots are on a circle C2 with a radius r_(c) of about 67.7 mminside the center line of the microwave waveguide 13 of the endlesscircular waveguide. The radius r_(c) of the circle C2 satisfies theabove mentioned equality.

With the apparatus of the above mentioned configuration, microwaves ofTE₁₀ mode introduced into the endless circular waveguide 13 aredistributed into two of the right and left at the E-junction andpropagate within the waveguide 13 at a guide wavelength longer than thewavelength in the free space. The distributed microwaves interfere witheach other to generate standing waves STW at every ½ of the guidewavelength. Microwaves introduced into the plasma processing chamber 9through the dielectric window 4 made of aluminium nitride from the slots33 provided at such positions as to maximize the current, i.e., at thecenters between adjoining two standing waves generate a plasma in thevicinity of the slots 33. When the electron plasma frequency of thegenerated plasma exceeds the power source frequency (for example, whenthe electron plasma frequency exceeds the power source frequency of 2.45GHz in the case where the electron density exceeds 7×10¹⁰ cm⁻³), theso-called cut-off in which microwaves can not propagate through theplasma is caused. Further, when the electron density increases and theskin depth δ defined by

 δ=(2/ωμ_(o)σ)^(1/2)

(wherein, ω is the angular frequency of a power source, μ_(o) the spacepermeability, and σ is the plasma conductivity) becomes sufficientlysmall (for example, when the electron density becomes 2×10¹² cm⁻³ ormore, the skin depth becomes 4 mm or less), the microwaves propagate asthe surface waves SW in the surface of the dielectric window 4.

Surface waves SW introduced via adjoining slots 33 interfere with eachother to generate surface standing waves SSTW at about every 20 mm. Thesurface standing waves SSTW leaked to the plasma processing chamberaccelerate electrons, thus generating a surface-wave interfered plasmaSIP.

The dielectric window 4 of aluminium nitride has a diameter 300 mm and athickness 12 mm. The endless circular waveguide has a 27 mm×96 mm innerwall cross section and a central diameter of 152 mm (the circumferentiallength l_(g) of the waveguide being three times the guide wavelengthλ_(g)). As the material of the endless circular waveguide 3, Al is usedentirely in order to suppress the propagation loss of microwaves.

In the H-plane of the endless circular waveguide 3, are formed slots 33for introducing microwaves into the plasma processing chamber 9. Theslots 33 each have a rectangular shape of 40 mm in length and 4 mm inwidth, and are formed radially at an interval of 60° in the total numberof six (6) with the centers of the slots being on the circle C2 of theradius of 67.7 mm. To the endless circular waveguide, are connected a 4Etuner, a directional coupler, an isolator, and a microwave power source(not shown) of frequency 2.45 GHz in this order.

The microwave plasma processing apparatus with the microwave applicatorshown in FIG. 19 was used to generate a plasma under the conditions ofan Ar flow rate of 500 sccm, a pressure of 1.33 Pa, and a microwavepower of 3.0 kW, and the plasma obtained was measured. The plasma wasmeasured as follows using a single probe method. The voltage applied tothe probe was varied within the range of −50 V to +100 V, and a currentflowing through the probe was measured by an I-V measuring device, andthe electron density, the electron temperature and the plasma potentialwere calculated from the thus obtained I-V curve by the Langmuir method.As a result, the electron density was 1.9×10¹²/cm³±3.1% (within φ 300plane) at 1.33 Pa, and it was confirmed that a high electron density,stable plasma was formed even in a low pressure region.

(Embodiment 10)

A microwave applicator of the microwave plasma processing apparatus inaccordance with a tenth embodiment of the present invention will bedescribed with reference to FIG. 20 in which the (waveguidecircumferential length)/(guide wavelength) ratio n^(g) is 4, theinterslot surface standing wave antinode number n¹ is 3 and 5, and thematerial of the dielectric window is aluminium nitride (dielectricconstant ∈_(w): 9.8). The configuration of the apparatus body is similarto that shown in FIGS. 16A to 16C.

In the present embodiment, the slots 33 are formed linearly anddiscontinuously in pairs such that the centers of the inner slots are ona circle C2 with a radius r_(c) of about 82.9 mm inside the center lineof the microwave waveguide 13 of the endless circular waveguide and thecenters of the outer slots are on a circle C5 with a radius r_(c) ofabout 127.2 mm outside the center line of the microwave waveguide 13,respectively. The radii r_(c) of the circles C2 and C5 each satisfiesthe above mentioned equality.

With the apparatus of the above mentioned configuration, microwaves ofTE₁₀ mode introduced into the endless circular waveguide 13 aredistributed into two of the right and left at the E-junction andpropagate within the waveguide 13 at a guide wavelength longer than thewavelength in the free space.

The distributed microwaves interfere with each other to generatestanding waves STW at every ½ of the guide wavelength in the waveguide.Microwaves introduced into the plasma processing chamber 9 through thedielectric window 4 from the slots 33 provided at such positions as tomaximize the current, i.e., at the centers between adjoining twostanding waves generate a plasma in the vicinity of the slots 33. Whenthe electron plasma frequency of the generated plasma exceeds the powersource frequency (for example, when the electron plasma frequencyexceeds the power source frequency of 2.45 GHz in the case where theelectron density exceeds 7×10¹⁰ cm⁻³), the so-called cut-off in whichmicrowaves can not propagate through the plasma is caused. Further, whenthe electron density increases and the skin depth δ defined byδ=(2/ωμ_(o)σ)^(1/2)(wherein, ω is the angular frequency of a power source, μ_(o) is thespace permeability, and σ is the plasma conductivity) becomessufficiently small (for example, when the electron density becomes2×10¹² cm⁻³ or more, the skin depth becomes 4 mm or less), themicrowaves propagate as the surface waves SW in the surface of thedielectric window 4.

Surface waves SW introduced via adjoining slots 33 interfere with eachother to generate surface standing waves SSTW at about every 20 mm. Thesurface standing waves SSTW leaked to the plasma processing chamberaccelerate electrons, thus generating a surface-wave interfered plasmaSIP.

The dielectric window 4 of aluminium nitride has a diameter 350 mm and athickness 13 mm. The endless circular waveguide has a 9 mm×96 mm innerwall cross section and a central diameter of about 202 mm (thecircumferential length 1 _(g) of the waveguide being four times theguide wavelength λ_(g)). As the material of the endless circularwaveguide 3, Al is used entirely in order to suppress the propagationloss of microwaves. In the H-plane of the endless circular waveguide 3,are formed slots 33 for introducing microwaves into the plasmaprocessing chamber 9. The slots 33 having their centers on the innercircle C2 with the radius 82.9 mm each have a rectangular shape of 40 mmin length and 4 mm in width and the slots 33 having their centers on theouter circle C5 with the radius 127.2 mm each have a rectangular shapeof 46 mm in length and 4 mm in width, and eight pairs of slots areformed radially in the total number of 16 at an interval of 45°. To theendless circular waveguide, are connected a 4E tuner, a directionalcoupler, an isolator, and a microwave power source (not shown) offrequency 2.45 GHz in this order.

The microwave plasma processing apparatus with the microwave applicatorshown in FIG. 20 was used to generate a plasma under the conditions ofan Ar flow rate of 500 sccm, a pressure of 1.33 Pa, and a microwavepower of 3.0 kW, and the plasma obtained was measured. The plasma wasmeasured as follows using a single probe method. The voltage applied tothe probe was varied within the range of −50 V to +100 V, and a currentflowing through the probe was measured by an I-V measuring device, andthe electron density, the electron temperature and the plasma potentialwere calculated from the thus obtained I-V curve by the Langmuir method.As a result, the electron density was 1.9×10¹²/cm³±2.2% (within φ 300plane) at 1.33 Pa, and it was confirmed that a high electron density,stable plasma was formed even in a low pressure region.

As described above, the shape of the circular waveguide used in thepresent invention is not limited to a circular ring but may be anellipsoidal, square, pentagonal ring, or the like, as long as it iscircular (or annular).

When a disk-like article such as a semiconductor wafer, optical disk,magnetic disk, or the like is to be processed, a circular ring shape ispreferable.

As the microwave applicator with a circular waveguide used in thepresent invention, it is also preferable to use an assembly of aconductive base member having a circular recess for forming a waveguideand a slotted flat plate.

It is also preferred that the inside of the waveguide is filled with adielectric to reduce the guide wavelength as the occasion demands. Assuch a dielectric, a resin such as tetrafluoroethylene, etc. ispreferably used.

The offset amount of the slots used in the present invention is suitablydetermined depending on the processing conditions used as described inEmbodiments 7 to 10. Especially, when the slotted flat plate 23 isconfigured to be interchangeable, it is possible to flexibly attend to achange in processing conditions.

The shape of the heterocentral slot used in the present invention inwhich the center of the slot is different from the center of thecircular waveguide may be a single rectangle perforation, or mayalternatively be a combination of plural perforations having a length of¼ to ⅜ of the guide wavelength and arranged discontinuously along aline, as long as the center of each slot is offset inside or outsidewith regard to the center line of the waveguide as described above.

As the material of the slotted flat plate and circular waveguide used inthe present invention, any conductor may be used, but an optimalmaterial is stainless steel plated with Al, Cu, or Ag/Cu that has a highconductivity in order to minimize the propagation loss of microwaves.

The direction of introducing microwaves into the circular waveguide usedin the present invention may be a direction in which microwaves can beintroduced parallel to the H-plane such as H-plane T junction ortangential introduction, or a direction in which microwaves can beintroduced perpendicularly to the H-plane such as E-plane T junction, aslong as it can efficiently introduce microwaves into the microwavepropagating space in the circular waveguide. Further, a distributor suchas shown by reference numeral 10 in FIG. 15 may be provided near theintroduction port. The slot interval in the microwave travellingdirection used in the present invention is optimally ½ or ¼ of the guidewavelength.

The microwave frequency used in the present invention may suitably beselected within the range of 0.8 GHz to 20 GHz.

As the dielectric of the microwave transmissive window used in thepresent invention, there can preferably be included quartz glass andother SiO₂-based glass, inorganic substances such as Si₃N₄, NaCl, KCl,LiF, CaF₂, BaF₂, Al₂O₃, AlN, MgO, etc., but films or sheets of organicsubstances such as polyethylene, polyester, polycarbonate, celluloseacetate, polypropylene, polyvinyl chloride, polyvinylidene chloride,polystyrene, polyamide, polyimide, etc. are also applicable.

In the present microwave plasma processing apparatus and method, amagnetic field generating means may be used. As the magnetic field usedin the present invention, although the mirror magnetic field isapplicable, the magnetron magnetic field is optimal which provides alarger magnetic flux density in a magnetic field in the vicinity of theslots than in a magnetic field in the vicinity of the article. As themagnetic field generating means other than coils, permanent magnets maybe used. When a coil is used, another cooling means such as a water- orair-cooling mechanism may be used to prevent overheating.

In addition, in order to further improve the quality of the processing,a surface of the article may be irradiated with ultraviolet light. Asthe light source, it is possible to use those which radiate a light thatis absorbed by the article or the gas adhering thereto, and it isappropriate to use excimer lasers and lamps, rare gas resonance linelamps, low-pressure mercury lamps, and the like.

The pressure inside the plasma generation chamber 9 of the presentinvention may be selected within the range of 1.33×10⁻² Pa to 1.33×10³Pa, and more preferably 1.33×10⁻¹ Pa to 1.33×10 Pa in the case of CVD,6.65×10⁻² Pa to 6.65 Pa in the case of etching, and 1.33×10 Pa to1.33×10³ Pa in the case of ashing.

The plasma processing method according to the present invention isdescribed with reference to FIGS. 10A to 10E.

As shown in FIG. 10A, on a surface of an article 101 such as a siliconsubstrate, is formed by a CVD apparatus or surface modifying apparatusan insulating film 102 made of an inorganic substance such as siliconoxide, silicon nitride, silicon oxynitride, aluminium oxide, tantalumoxide, etc. or an organic substance such as tetrafluoroethylene,polyarylether, etc.

As shown in FIG. 10B, a photo resist is applied thereon and baking iscarried out to form a photo resist layer 103.

As shown in FIG. 10C, a hole pattern latent image is formed by analigner and developed to form a photo resist pattern 103′ with holes104.

As shown in FIG. 10D, the insulating film 102 under the photo resistpattern 103′ is etched by an etching apparatus to form holes 105.

As shown in FIG. 10E, the photo resist pattern 103′ is ashed by use ofan ashing apparatus to be removed.

Thus, a structure with a holed insulating film is obtained.

When a conductor or the like is further deposited in the holes, it ispreferred that the inside of the holes is previously cleaned by acleaning apparatus or the like.

Further, the plasma processing apparatuses according to the presentinvention described above by referring to FIGS. 1 to 9, 16A to 16C, and18 to 20 are available as at least one of the CVD apparatus, surfacemodifying apparatus, etching apparatus and ashing apparatus used in theabove mentioned steps.

FIGS. 11A to 11C illustrates another plasma processing method accordingto the present invention.

As shown in FIG. 11A, there is formed a pattern (here, line and space)of a conductor comprised of a metal such as aluminium, copper,molybdenum, chromium, or tungsten, or an alloy containing at least oneof the metals as a main component or polycrystal silicon is formed.

As shown in FIG. 11B, an insulating film 107 is formed by a CVDapparatus or the like.

After a photo resist pattern (not shown) is formed, holes 108 are formedin the insulating film 107 by an etching apparatus.

The photo resist pattern is removed by an ashing apparatus or the liketo provide a structure as shown in FIG. 11C.

Further, the plasma processing apparatus of the present invention can beused as the above mentioned CVD apparatus, etching apparatus and ashingapparatus, but is not limitedly applied thereto as described below.

In formation of a deposited film according to the present microwaveplasma processing method, suitable selection of the gases used enablesefficient formation of various deposited films such as an insulatingfilm of Si₃N₄, SiO₂, Ta₂O₅, TiO₂, TiN, Al₂O₃, AlN, MgF₂, AlF₃,fluorocarbons, etc.; a semiconductor film of a-Si (amorphous silicon),poly-Si (polysilicon), SiC, GaAs, etc.; and a metal film of Al, W, Mo,Ti, Ta, etc.; amorphous carbon, diamond-like carbon, diamond, or thelike.

The base member (substrate) of an article processed by the presentplasma processing method may be semiconducting, conductive orinsulating. Specific examples thereof include semiconductor substratessuch as an Si wafer, SOI wafer, or the like.

As the conductive substrate, there can be included metals such as Fe,Ni, Cr, Al, Mo, Au, Nb, Ta, V, Ti, Pt, Pb, etc., and alloys thereof suchas brass, stainless steel, etc.

As the insulating substrate, there can be included quartz glass andother glasses; inorganic substances such as Si₃N₄, NaCl, KCl, LiF, CaF₂,BaF₂, Al₂O₃, AlN, MgO, etc.; and films or sheets of organic substancessuch as polyethylene, polyester, polycarbonate, cellulose acetate,polypropylene, polyvinyl chloride, polyvinylidene chloride, polystyrene,polyamide, polyimide, etc.

As the gases used in the case of forming a thin film on a substrate bythe CVD process, generally known gases can be used.

Specifically, when a thin film of an Si-based semiconductor such asa-Si, poly-Si, or SiC is to be formed, there can be included those whichare in a gaseous state at ordinary temperature and pressure or which aregassified easily, for example, inorganic silanes such as SiH₄ or Si₂H₆;organic silanes such as tetraethylsilane (TES), tetramethylsilane (TMS),dimethylsilane (DMS), dimethyldifluorosilane (DMDFS), ordimethyldichlorosilane (DMDCS); or halosilanes such as SiF₄, Si₂F₆,Si₃F₈, SiHF₃, SiH₂F₂, SiCl₄, Si₂Cl₆, SiHCl₃, SiH₂Cl₂, SiH₃Cl, orSiCl₂F₂. In addition, as an additional gas or a carrier gas that may bemixed with the Si material gas and introduced, there may be included H₂,He, Ne, Ar, Kr, Xe, and Rn.

As the material containing Si atoms used for formation of a thin filmbased on an Si compound such as Si₃N₄ or SiO₂, the following materialsthat maintain a gaseous state at ordinary temperature and pressure orthat are gassified easily using a vaporizer or a bubbler can be used:inorganic silanes such as SiH₄ or Si₂H₆; organic silanes such astetraetoxysilane (TEOS), tetrametoxysilane (TMOS),octamethylcyclotetrasilane (OMCTS), dimethyldifluorosilane (DMDFS), ordimethyldichlorosilane (DMDCS); or halosilanes such as SiF₄, Si₂F₆,Si₃F₈, SiHF₃, SiH₂F₂, SiCl₄, Si₂Cl₆, SiHCl₃, SiH₂Cl₂, SiH₃Cl, orSiCl₂F₂. In addition, as a nitrogen or an oxygen material gas that maybe simultaneously introduced, there can be included N₂, NH₃, N₂H₄,hexamethyldisilazane (HMDS), O₂, O₃, H₂O, NO, N₂O, NO₂, and so on.

The material containing metal atoms which is used to form a thin metalfilm such as of Al, W, Mo, Ti, Ta, or the like includes organic metalssuch as trimethyl aluminium (TMAl), triethyl aluminium (TEAl),triisobutyl aluminium (TIBAl), dimethyl aluminium hydride (DMAlH),tungsten carbonyl (W(CO)₆), molybdenum carbonyl (Mo(CO)₆), trimethylgallium (TMGa), and triethyl gallium (TEGa); and halogenated metals suchas AlCl₃, WF₆, TiCl₃, and TaCl₅. In this case, as an additional orcarrier gas which may be mixed with the above Si material gas, H₂, He,Ne, Ar, Kr, Xe, Rn, and so on may be included.

The material containing metal atoms which is used to form a thin metalcompound film such as of Al₂O₃, AlN, Ta₂O₅, TiO₂, TiN, WO₃, or the likeincludes organic metals such as trimethyl aluminium (TMAl), triethylaluminium (TEAl), triisobutyl aluminium (TIBAl), dimethyl aluminiumhydride (DMAlH), tungsten carbonyl (W(CO)₆), molybdenum carbonyl(Mo(CO)₆), trimethyl gallium (TMGa), and triethyl gallium (TEGa); andhalogenated metals such as AlCl₃, WF₆, TiCl₃, and TaCl₅. In this case,as an oxygen or a nitrogen material gas that may be simultaneouslyintroduced includes O₂, O₃, H₂O, NO, N₂O, NO₂, N₂, NH₃, N₂H₄, andhexamethyldisilazane (HMDS).

When a carbon film such as of amorphous carbon, diamond-like carbon,diamond, or the like is to be formed, a carbon-containing gas such asCH₄, C₂H₆, etc. may preferably be used.

When a fluorocarbon film is to be formed, a fluorine andcarbon-containing gas such as CF₄, C₂F₆, etc. may preferably be used.

As the etching gas for etching a surface of a substrate, there may beincluded F₂, CF₄, CH₂F₂, C₂F₆, C₄F₈, CF₂Cl₂, SF₆, NF₃, Cl₂, CCl₄,CH₂Cl₂, C₂Cl₆, or the like.

As the ashing gas for ashing and removing organic components on asurface of a substrate such as a photo resist, there may be included O₂,O₃, H₂O, N₂, NO, N₂O, NO₂, and so on.

Further, in the case of the cleaning, the etching or ashing gas listedabove, or hydrogen gas or an inactive gas may be used.

In addition, when the present microwave plasma processing apparatus andmethod is applied to surface modification, appropriate selection of thegas used enables the oxidation or nitridation treatment of a substrateor a surface layer consisting of, e.g., Si, Al, Ti, Zn, or Ta or thedoping treatment with B, As, or P. Furthermore, the present inventioncan be applied to the cleaning process. In this case, it can be used tocleaning of oxides, organic substances, or heavy metals.

As the oxidizing gas used for surface treatment by oxidation of asubstrate, there may be included O₂, O₃, H₂O, NO, N₂O, NO₂, or the like.In addition, the nitriding gas used for surface treatment by nitridationof a substrate includes N₂, NH₃, N₂H₄, and hexamethyldisilazane (HMDS).

As a cleaning/ashing gas used when an organic substance on the surfaceof a substrate is cleaned or when an organic component on the surface ofa substrate, such as a photo resist is removed by ashing, O₂, O₃, H₂O,H₂, NO, N₂O, N₂, or the like may be included. In addition, as a cleaninggas used when an inorganic substance on the surface of a substrate iscleaned, F₂, CF₄, CH₂F₂, C₂F₆, C₄F₈, CF₂Cl₂, SF₆, NF₃, or the like maybe included.

The present invention is specifically described below with reference toexamples, but the present invention is not limited to these examples.

EXAMPLE 1

In this example, an apparatus with the configuration such as shown inFIGS. 1 and 2 was produced and a plasma was generated therein.

In an aluminium conductive member, was formed a circular groove whichforms an endless circular waveguide 13. The endless circular waveguidehas a rectangular section of 27 mm in height and 96 mm in width as asection perpendicular to the microwave travelling direction, and havinga circumferential length three times the guide wavelength and a centraldiameter of 152 mm.

In a conductive flat plate, were formed six rectangular slots of 42 mmin length and 4 mm in width at an interval of ½ of the guide length toproduce a slotted flat plate 23 made of aluminium. At this time, thecenters of the slots were offset inside by 24 mm with regard to thecenter line of the waveguide 13.

The conductive member and the slotted flat plate were assembled into amicrowave applicator such as shown in FIG. 1.

Anhydrous synthetic quartz glass was worked to form a disc with adiameter 299 mm and a thickness 12 mm to be used as the dielectricwindow 4.

For the purpose of experiment, a probe was arranged in the space 9, thenthe inside of the space 9 was exhausted, and argon gas was introduced at500 sccm through the gas supply passage 7.

The conductance valve of the exhaust system and the mass flow controllerof the gas supply system were adjusted to maintain the pressure insidethe space 9 at 1.33 Pa.

Microwaves of 2.45 GHz and 3.0 kW was introduced in the TE₁₀. mode intothe microwave applicator 3 through the waveguide 13 via a 4E tuner, adirectional coupler and an isolator.

Using a single probe method, the voltage applied to the probe was variedwithin a range of −50 V to +100 V, while the current flowing through theprobe was measured, thus obtaining an I-V curve and calculate theelectron density. As a result, the electron density was 2.1×10¹²/cm³within a plane of 300 in diameter with the uniformity of the electrondensity (represented by dispersion) being ±2.7%.

Next, when the pressure was raised to 133 Pa and the electron densitywas measured in the same manner as above, it was 9.6×10¹¹/cm³ with theuniformity of the electron density being ±5.4%.

From the above, it was confirmed that a high density plasma was formednear the lateral center of the space 9 even in a high pressure region.

EXAMPLE 2

In this example, an apparatus with the configuration such as shown inFIGS. 3 and 4 was produced and a plasma was generated therein.

The slotted flat plate used in Example 1 was replaced with a flat platesuch as shown in FIG. 4.

In an aluminium flat plate, were formed at the inside positions sixrectangular slots of 42 mm in length and 4 mm in width at an equalinterval. The offset amount was 23 mm.

Further, there were formed at the outside positions six rectangularslots of 42 mm in length and 4 mm in width at an equal interval. Theoffset amount was 23 mm.

Thus, there were formed six pairs of discontinuous linear slots at aninterval of one half of the guide wavelength.

The interval between a pair of slots on the same line was 4 mm and theangle formed by adjacent discontinuous linear slots was 60°.

Further, anhydrous synthetic quartz glass was worked to form thedisc-like dielectric window 4 with a diameter 299 mm and a thickness 16mm.

The procedure of Example 1 was followed to calculate the electrondensity of a plasma.

When the pressure was 1.33 Pa, the electron density was 1.9×10¹²/cm³with the uniformity ±2.7%.

When the pressure was 133 Pa, the electron density was 8.7×10¹¹/cm³ withthe uniformity ±5.6%.

EXAMPLE 3

The microwave plasma processing apparatus shown in FIGS. 1 and 2 wasused to carry out ashing of a photo resist by the following procedure.

As the article W, was used a silicon substrate (200 mm in diameter)immediately after an insulating film of silicon oxide under a photoresist pattern was etched to form via holes. First, the Si substrate wasput on the holding means 2, and the inside of the container 1 wasevacuated via the exhaust system to reduce the pressure down to1.33×10⁻³ Pa. Oxygen gas was introduced at a flow rate of 2 slm into thecontainer 1 via the processing gas supply port 17. Then, the conductancevalve 28 provided in the exhaust system was adjusted to maintain theinside of the container 1 at 133 Pa. A power of 1.5 kW and 2.45 GHz fromthe microwave power source 6 was supplied into the container 1 throughthe microwave applicator 3 to generate a plasma in the space 9. At thistime, the oxygen gas introduced via the processing gas supply port 17was converted to ozone in the space 9, which was then transported towardthe Si substrate W to oxidize the photo resist on the substrate, thusvaporizing the photo resist to be removed. After ashing, the ashingspeed and the charge density on the surface of the substrate wereevaluated.

The ashing speed and uniformity obtained was as very high as 6.6 μm/min±4.5%, and the surface charge density was as sufficiently low as−1.3×10¹¹/cm².

EXAMPLE 4

The microwave plasma processing apparatus shown in FIGS. 3 and 4 wasused to carry out ashing of a photo resist.

The article used and the processing procedure are the same as in Example3.

The ashing speed and uniformity obtained was 6.4 μm/min±3.4%, and thesurface charge density was as sufficiently low as −1.4×10¹¹/cm².

EXAMPLE 5

The microwave plasma processing apparatus shown in FIGS. 1 and 2 wasused to form a silicon nitride film serving to protect a semiconductorelement by the following procedure.

The article W was a P-type single crystal silicon substrate (faceorientation <100>; resistivity: 10 Ωcm) with an insulation filmcomprised of silicon oxide on which an Al wiring pattern with line andspace each of 0.5 μm was formed. First, the silicon substrate was put onthe holding means 2, and the inside of the container 1 was thenevacuated via the exhaust system to reduce the pressure down to1.33×10⁻⁵ Pa. Subsequently, a heater (not shown) provided in the holdingmeans 2 was energized to heat the silicon substrate to 300° C., and thesubstrate was maintained at this temperature. Nitrogen gas at a flowrate of 600 sccm and monosilane gas at a flow rate of 200 sccm wereintroduced into the container 1 via the processing gas supply port 17.Then, the conductance valve 28 provided in the exhaust system wasadjusted to maintain the inside of the container 1 at 2.66 Pa.Subsequently, a power of 3.0 kW and 2.45 GHz from the microwave powersource 6 was introduced via the microwave applicator 3. Thus, a plasmawas generated in the space 9. At this time, the nitrogen gas introducedvia the processing gas supply port 17 was excited, decomposed or ionizedin the space 9 to form an active species, which was then transportedtoward the silicon substrate to react with the monosilane gas, therebyforming a silicon nitride film in 1.0 μm thickness on the siliconsubstrate. The film formation speed and the film quality such as stresswere evaluated. For the stress, the change in the amount of the warpageof the substrate was measured before and after the film formation usinga laser interferometer Zygo (trade name).

The formation speed and uniformity of the silicon nitride film obtainedwas 510 nm/min±2.5, and the stress was 1.2×10⁹ dyne/cm² (compression),the leak current was 1.2×10⁻¹⁰A/cm², and the dielectric strength was 9MV/cm, and the film was therefore confirmed to be very excellent.

EXAMPLE 6

The microwave plasma processing apparatus shown in FIGS. 3 and 4 wasused to form a silicon oxide and a silicon nitride films serving as ananti-reflection film for a plastic lens by the following procedure.

The article W was a plastic convex lens of a diameter 50 mm. First, thelens was put on the holding means 2, and the inside of the container 1was evacuated via the exhaust system to reduce the pressure down to1.33×10⁻⁵ Pa. Nitrogen gas at a flow rate of 160 sccm and monosilane gasat a flow rate of 100 sccm were introduced into the container 1 via theprocessing gas supply port 17. Then, the conductance valve 28 providedin the exhaust system was adjusted to maintain the inside of thecontainer 1 at 9.32×10⁻¹ Pa. Subsequently, a power of 3.0 kW and 2.45GHz from the microwave power source 6 was supplied into the container 1through the microwave applicator 3 to generate a plasma in the space 9.At this time, the nitrogen gas introduced via the processing gas supplyport 17 was excited, decomposed or ionized in the space to form anactive species such as nitrogen atoms, which was then transported towardthe lens to react with the monosilane gas, thereby forming a siliconnitride film in a 21 nm thickness on the surface of the lens.

Next, oxygen gas at a flow rate of 200 sccm and monosilane gas at a flowrate of 100 sccm were introduced into the container 1 via the processinggas supply port 17. Then, the conductance valve 28 provided in theexhaust system was adjusted to maintain the inside of the container 1 at1.33×10⁻¹ Pa. Subsequently, a power of 2.0 kW and 2.45 GHz from themicrowave power source 6 was supplied into the container 1 through themicrowave applicator 3 to generate a plasma in the space 9. At thistime, the thus introduced oxygen gas was excited and decomposed in thespace 9 to form an active species such as oxygen atoms, which was thentransported toward the lens to react with the monosilane gas, therebyforming a silicon oxide film in a 86 nm thickness on the lens. The filmformation speed and the reflection characteristic were evaluated.

The formation speeds and uniformities of the silicon nitride and siliconoxide films as obtained were 320 nm/min±2.2% and 350 nm/min±2.6%,respectively, and the reflectance in the vicinity of 500 nm was 0.3%,and the film was thus confirmed to have very excellent opticalcharacteristics.

EXAMPLE 7

The microwave plasma processing apparatus shown in FIGS. 3 and 4 wasused to form a layer insulation film of a semiconductor element by thefollowing procedure.

The article W was a P-type single crystal silicon substrate (faceorientation <100>; resistivity: 10 Ωcm) having formed on the top portionan Al pattern of line and space of 0.5 μm each. First, the siliconsubstrate was put on the holding means 2. The inside of the container 1was then evacuated via the exhaust system to reduce the pressure down to1.33×10⁻⁵ Pa. Subsequently, a heater provided in the holding means wasenergized to heat the silicon substrate to 300° C., and the substratewas maintained at this temperature. Oxygen gas at a flow rate of 500sccm and monosilane gas at a flow rate of 200 sccm were introduced intothe container 1 via the processing gas supply port 17. Then, theconductance valve 28 provided in the exhaust system was adjusted tomaintain the inside of the container 1 at 4.00 Pa. Subsequently, ahigh-frequency power of 300 W and 13.56 MHz was applied to the holdingmeans 2 via the bias voltage application means provided in the holdingmeans, while a power of 2.0 kW and 2.45 GHz from the microwave powersource 6 was supplied into the container 1 through the microwaveapplicator 3, thus generating a plasma in the space 9. The oxygen gasintroduced via the processing gas supply port 17 was excited anddecomposed in the space 9 to form an active species, which was thentransported toward the silicon substrate to react with the monosilanegas, thereby forming a silicon oxide film in a 0.8 μm thickness on thesilicon substrate. At this time, ion species were accelerated by the RFbias to be incident to the substrate and to cut the silicon oxide filmon the Al pattern, thereby improving the flatness. Then, the filmformation speed, uniformity, dielectric strength, and step coverage wereevaluated. The step coverage was evaluated by observing a cross sectionof the silicon oxide film formed on the Al pattern with a scanningelectron microscope (SEM) to check presence of voids.

The formation speed and uniformity of the silicon oxide film thusobtained was 240 nm/min±2.5%, and the dielectric strength was 8.5 MV/cmand no voids were found. Therefore, the film was confirmed to beexcellent.

EXAMPLE 8

The microwave plasma processing apparatus shown in FIGS. 3 and 4 wasused to etch a layer insulation film of a semiconductor element by thefollowing procedure.

The article W was a P-type single crystal silicon substrate (faceorientation <100>; resistivity: 10 Ωcm) having formed on an Al patternof line and space of 0.18 μm an insulating film comprised of siliconoxide in 1 μm thickness and a photo resist pattern further thereon.First, after the silicon substrate was put on the holding means 2, theinside of the container 1 was evacuated via the exhaust system to reducethe pressure down to 1.33×10⁻⁵ Pa. C₄F₈ gas at a flow rate of 100 sccmwas introduced into the container 1 via the processing gas supply port17. Then, the conductance valve 28 provided in the exhaust system wasadjusted to maintain the inside of the container 1 at 1.33 Pa.Subsequently, a high-frequency power of 300 W and 13.56 MHz was appliedto the holding means 2 via the bias voltage application means providedin the holding means, while a power of 2.0 kW and 2.45 GHz from themicrowave power source 6 was supplied into the container 1 through themicrowave applicator 3, thus generating a plasma in the space 9. TheC₄F₈ gas introduced into the container 1 via the processing gas supplyport 17 was excited and decomposed in the space 9 to form an activespecies, which was then transported toward the silicon substrate, whereions accelerated by a self bias etched the silicon oxide insulating filmto form holes. A cooler (not shown) provided in the holding means 2prevented the temperature of the substrate from increasing above 80° C.After etching, the etch rate, etch selectivity, and etched shape wereevaluated. The etched shape was evaluated by using a scanning electronmicroscope (SEM) to observe a cross section of the etched silicon oxidefilm.

The etch rate and uniformity and the etch selectivity to polysiliconwere 540 nm/min±2.2% and 20, respectively, and it was confirmed that theholes showed almost vertical side surfaces, and that the microloadingeffect was small.

EXAMPLE 9

The plasma processing apparatus shown in FIGS. 3 and 4 was used to ash aphoto resist on a wafer of 200 in diameter.

As the microwave applicator, there was used one having such aconfiguration that the circumferential length was twice the guidelength, and that four pairs of discontinuous linear slots were formed atan interval of one half of the guide wavelength.

EXAMPLE 10

The plasma processing apparatus shown in FIGS. 3 and 4 was used to etchan insulation film comprised of silicon oxide on a surface of a wafer of300 mm in diameter.

As the microwave applicator, there was used one having such aconfiguration that the circumferential length was 4 times the guidelength, and that eight pairs of discontinuous linear slots were formedat an interval of one half of the guide wavelength.

EXAMPLE 11

The microwave plasma processing apparatus shown in FIGS. 5 and 6 wasused to carry out ashing of a photo resist by the following procedure.

As the article W, was used a silicon substrate (φ8 inches) immediatelyafter a layer insulating SiO₂ film was etched to form via holes. First,the Si substrate was put on the holding means 2, and the inside of thecontainer 1 was evacuated via the exhaust system (not shown) to reducethe pressure down to about 1.33×10⁻³ Pa. Oxygen gas as the plasmaprocessing gas was introduced at a flow rate of 2 slm into the container1. Then, the conductance valve (not shown) provided in the exhaustsystem (not shown) was adjusted to maintain the inside of the container1 at about 2.66×10² Pa. A power of 1.5 kW from a microwave power sourceof 2.45 GHz was supplied into the container 1 through the microwaveapplicator 3 to generate a plasma in the container 1. At this time, apart of the oxygen gas as introduced was converted to ozone in thecontainer 1, which was then transported toward the silicon substrate tooxidize the photo resist on the silicon substrate, whereby the photoresist was vaporized to be removed. At this time, the ashing speed andthe charge density on the surface of the substrate were evaluated.

The ashing speed obtained was as significantly high as 8.6 μm/min±8.5%,and the surface charge density was as sufficiently low as −1.3×10¹¹/cm².

EXAMPLE 12

The microwave plasma processing apparatus shown in FIG. 7 was used tocarry out ashing of a photo resist by the following procedure.

As the article W, was used a silicon substrate (φ8 inches) immediatelyafter a layer insulating SiO₂ film was etched to form via holes. First,the Si substrate was put on the holding means 2, and the inside of thecontainer 1 was evacuated to reduce the pressure down to about 1.33×10⁻³Pa. Oxygen gas was introduced at a flow rate of 2 slm into the container1. Then, the inside of the container 1 was maintained at about 2.66×10²Pa. A power of 1.5 kW from a microwave power source of 2.45 GHz wassupplied into the container 1 through the microwave applicator 3 togenerate a plasma in the container 1. At this time, the oxygen gas asintroduced was converted to ozone, which was then transported toward thesubstrate to oxidize the photo resist on the substrate, whereby thephoto resist was vaporized to be removed. At this time, the ashing speedand the charge density on the surface of the substrate were evaluated.

The ashing speed obtained was as significantly high as 8.4 μm/min±7.4%,and the surface charge density was as sufficiently low as −1.4×10¹¹/cm².

EXAMPLE 13

The microwave plasma processing apparatus shown in FIGS. 5 and 6 wasused to form a silicon nitride film serving to protect a semiconductorelement by the following procedure.

The article W was a P-type single crystal silicon substrate (faceorientation <100>; resistivity: 10 Ωcm) with a layer insulation SiO₂film on which an Al wiring pattern (line and space: 0.5 μm) wasprovided. First, the silicon substrate was put on the holding means 2,and the inside of the container 1 was then evacuated to reduce thepressure down to about 1.33×10⁻⁵ Pa. Subsequently, the heater 114 wasenergized to heat the silicon substrate to 300° C., and the substratewas maintained at this temperature. Nitrogen gas at a flow rate of 600sccm and monosilane gas at a flow rate of 200 sccm were introduced intothe container 1, and the inside of the container 1 was maintained atabout 2.66 Pa. Subsequently, a microwave power of 3.0 kW and 2.45 GHzwas introduced into the container via the microwave applicator 3 togenerated a plasma. At this time, the nitrogen gas formed activespecies, which was then transported toward the silicon substrate toreact with the monosilane gas, thereby depositing a silicon nitride filmin 1.0 μm thickness on the silicon substrate. As to the deposited film,the film formation speed and the film quality such as stress wereevaluated. For the stress, the change in the amount of the warpage ofthe substrate was measured before and after the film formation using alaser interferometer Zygo (trade name).

The formation speed of the silicon nitride film obtained was assignificantly high as 510 nm/min, and the stress was 1.2×10⁹ dyne/cm²(compression), the leak current was 1.2×10⁻¹⁰A/cm², and the dielectricstrength was 9 MV/cm, and the film was therefore confirmed to be veryexcellent.

EXAMPLE 14

The microwave plasma processing apparatus shown in FIG. 7 was used toform a silicon oxide and a silicon nitride films serving as ananti-reflection film for a plastic lens by the following procedure.

The article W was a plastic convex lens of a diameter 50 mm. First, thelens was put on the holding means 2, and the inside of the container 1was evacuated to reduce the pressure down to about 1.33×10⁻⁵ Pa.Nitrogen gas at a flow rate of 160 sccm and monosilane gas at a flowrate of 100 sccm were introduced into the container 1, and the inside ofthe container 1 was maintained at about 0.93 Pa. Subsequently, a powerof 3.0 kW and 2.45 GHz was supplied into the container 1 through themicrowave applicator 3 to generate a plasma in the container 1. Asilicon nitride film was formed in a 21 nm thickness on the lens.

Next, oxygen gas at a flow rate of 200 sccm and monosilane gas at a flowrate of 100 sccm were introduced into the container 1. Then, the insideof the container 1 was maintained at about 0.133 Pa. Subsequently, apower of 2.0 kW and 2.45 GHz was supplied into the container 1 togenerate a plasma in the space 9. At this time, the thus introducedoxygen gas was excited and decomposed in the space 9 to form activespecies such as oxygen atoms or radicals, which was then transportedtoward the lens to react with the monosilane gas, thereby depositing asilicon oxide film in a 86 nm thickness on the lens.

The formation speeds and uniformities of the silicon nitride and siliconoxide films as obtained were as good as 320 nm/min and 350 nm/min,respectively, and the reflectance in the vicinity of 500 nm was 0.3%,and the film was thus confirmed to have very excellent reflectancecharacteristics.

EXAMPLE 15

The microwave plasma processing apparatus shown in FIG. 8 was used toform a silicon oxide film for layer insulation of a semiconductorelement by the following procedure.

The article W was a P-type single crystal silicon substrate (faceorientation <100>; resistivity: 10 Ωcm) having formed on the top portionan Al pattern (line and space: 0.5 μm). First, the silicon substrate wasput on the holding means 2. The inside of the container 1 was thenevacuated to reduce the pressure down to about 1.33×10⁻⁵ Pa.Subsequently, the heater 114 was energized to heat the silicon substrateto 300° C., and the substrate was maintained at this temperature. Oxygengas at a flow rate of 500 sccm and monosilane gas at a flow rate of 200sccm were introduced into the container 1, and the inside of thecontainer 1 was maintained at about 3.99 Pa. Subsequently, an RF powerof 300 W and 13.56 MHz was applied to the holding means 2, while a powerof 2.0 kW and 2.45 GHz was supplied into the container 1 through themicrowave applicator 3, thus generating a plasma in the space 9. Theoxygen gas as introduced was excited, decomposed or ionized to form anactive species, which was then transported toward the silicon substrateto react with the monosilane gas, thereby depositing silicon oxide. Inthis example, the ion species has a function of being accelerated by theRF bias to be incident to the substrate and to cut the film on thepattern, thereby improving the flatness of the film. As to the siliconoxide film formed in a 0.8 μm thickness on the substrate, the filmformation speed, uniformity, dielectric strength, and step coverage wereevaluated. The step coverage was evaluated by observing a cross sectionof the silicon oxide film formed on the Al pattern with a scanningelectron microscope (SEM) to check presence of voids.

The formation speed and uniformity of the silicon oxide film thusobtained was as good as 240 nm/min±2.5%, and the dielectric strength was8.5 MV/cm and no voids were found. Therefore, the film was confirmed tobe excellent.

EXAMPLE 16

The microwave plasma processing apparatus shown in FIG. 9 was used toetch a layer insulation SiO₂ film of a semiconductor element by thefollowing procedure.

The article W was a P-type single crystal silicon substrate (faceorientation <100>; resistivity: 10 Ωcm) having formed on an Al pattern(line and space: 0.35) an layer insulation SiO₂ film in 1 μm thickness.First, after the silicon substrate was put on the holding means 2, theinside of the container 1 was evacuated via an exhaust system (notshown) to reduce the pressure down to about 1.33×10⁻⁵ Pa. C₄F₈ gas at aflow rate of 100 sccm was introduced into the container 1, and theinside of the container 1 was maintained at 1.33 Pa. Subsequently, an RFpower of 300 W and 13.56 MHz was applied to the holding means 2, while amicrowave power of 2.0 kW and 2.45 GHz was supplied into the container 1through the microwave applicator 3, thus generating a plasma in thespace 9. The C₄F₈ gas as introduced was excited, decomposed or ionizedin the space 9 to form an active species, which was then transportedtoward the silicon substrate, where ions accelerated by a self biasetched the layer insulation SiO₂ film. The cooler 414 prevented thetemperature of the substrate from increasing above 80° C. In theetching, the etch rate, etch selectivity, and etched shape wereevaluated. The etched shape was evaluated by using a scanning electronmicroscope (SEM) to observe a cross section of the etched silicon oxidefilm.

The etch rate and the etch selectivity to polysilicon were as good as540 nm/min and 20, respectively, and it was confirmed that the etchedshape was almost vertical, and that the microloading effect was small.

EXAMPLE 17

The microwave plasma processing apparatus shown in FIG. 9 was used toetch a polysilicon film for a gate electrode of a semiconductor elementby the following procedure.

As the article W, was provided a P-type single crystal silicon substrate(face orientation <100>; resistivity: 10 Ωcm) having a polysilicon filmformed on the top portion thereof. First, after the silicon substratewas put on the holding means 2, the inside of the container 1 wasevacuated to reduce the pressure down to about 1.33×10⁻⁵ Pa. C₄F₈ gas atthe flow rate of 100 sccm and oxygen at the flow rate of 20 sccm wereintroduced into the container 1, and the inside of the container 1 wasmaintained at about 0.67 Pa. Subsequently, a high-frequency power of 300W and 4000 kHz was applied to the holding means 2, while a microwavepower of 1.5 kW and 2.45 GHz was supplied into the container 1 throughthe microwave applicator 3, thus generating a plasma in the space 9. TheC₄F₈ gas and oxygen as introduced were excited, decomposed or ionized inthe space 9 to form an active species, which was then transported towardthe silicon substrate, where ions accelerated by a self bias etched thepolysilicon film. During the processing, the cooler 414 prevented thetemperature of the substrate from increasing above 80° C. The etch rate,etch selectivity, and etched shape in the etching were evaluated. Theetched shape was evaluated by using a scanning electron microscope (SEM)to observe a cross section of the etched polysilicon film.

The etch rate and the etch selectivity to SiO₂ were as good as 750nm/min and 29, respectively, and it was confirmed that the etched shapewas vertical, and that the microloading effect was small.

EXAMPLE 18

The microwave plasma processing apparatus with the microwave applicatorshown in FIG. 18 was used to carry out ashing of a photoresist by thefollowing procedure.

As the article W, was used a silicon (Si) substrate (φ 8 inches)immediately after an interlayer SiO₂ film was etched to form via holes.

First, after the Si substrate was put on the support means 2 and heatedto 250° C. using a heater as the temperature adjusting means 114, theplasma processing chamber 9 was evacuated via the exhaust system (18,28) to reduce the pressure down to 1.33×10⁻³ Pa. Oxygen gas wasintroduced at a flow rate of 500 sccm into the plasma generation chamber9 via the plasma processing gas supply port 7.

Then, the conductance valve 28 provided between the plasma processingchamber and the exhaust means 18 was adjusted to maintain the inside ofthe plasma processing chamber 9 at 40 Pa. A power of 1.5 kW from themicrowave power source MW of 2.45 GHz was supplied into the plasmaprocessing chamber 9 through the endless circular waveguide.

Thus, a plasma was generated in the plasma processing chamber 9. At thistime, the oxygen gas introduced via the plasma processing gas supplyport 7 was excited, decomposed and reacted to be converted to oxygenradicals in the plasma processing chamber 9, which were then transportedtoward the Si substrate W to oxidize the photoresist on the substrateand exhausted to the exhaust system side to be removed. After ashing,the ashing speed and the charge density on the surface of the substratewere evaluated.

The ashing speed and uniformity obtained was as very good as 5.6μm/min±4.5%, and the surface charge density was as sufficiently low as−1.3×10¹¹/cm².

EXAMPLE 19

The microwave plasma processing apparatus with the microwave applicatorshown in FIG. 17 was used to carry out ashing of a photoresist.

As the article W, was used a silicon (Si) substrate (φ 8 inches)immediately after an interlayer SiO₂ film was etched to form via holes.

First, after the Si substrate was put on the support means 2, the plasmaprocessing chamber 9 was evacuated via the exhaust system (18, 28) toreduce the pressure down to 1.33×10⁻³ Pa. Oxygen gas was introduced at aflow rate of 1 slm into the plasma processing chamber 9 via the plasmaprocessing gas supply port 7.

Then, the conductance valve 28 provided between the plasma processingchamber and the exhaust means 18 was adjusted to maintain the inside ofthe plasma processing chamber 9 at 80 Pa. A microwave power of TE₁₀ modeand 1.5 kW from the microwave power source MW of 2.45 GHz was suppliedinto the plasma processing chamber 9 through the endless circularwaveguide.

Thus, a plasma was generated in the plasma processing chamber 9. At thistime, the oxygen gas introduced via the plasma processing gas supplyport 7 was excited, decomposed and reacted to be converted to oxygenradicals in the plasma processing chamber 9, which were then transportedtoward the Si substrate W to oxidize the photoresist on the substrate,thus vaporizing the photoresist to be removed. After ashing, the ashingspeed and the charge density on the surface of the substrate wereevaluated.

The ashing speed and uniformity obtained was very large as 5.4μm/min±3.4%, and the surface charge density was as sufficiently low as−1.4×10¹¹/cm².

EXAMPLE 20

The microwave plasma processing apparatus with the microwave applicatorshown in FIG. 18 was used to form a silicon nitride film serving toprotect a semiconductor element by the following procedure.

As the article W was used a P-type single crystal silicon substrate(face orientation <100>; resistivity: 10 Ωcm) with an interlayer SiO₂film on which an Al wiring pattern with line and space each of 0.5 μmwas formed.

First, after the silicon substrate was put on the support means 2, theplasma processing chamber 9 was evacuated via the exhaust system (18,28) to reduce the pressure down to 1.33×10⁻⁵ Pa.

Subsequently, a heater as the temperature adjusting means 114 wasenergized to heat the silicon substrate to 300° C., and the substratewas maintained at this temperature. Nitrogen gas at a flow rate of 600sccm and monosilane gas at a flow rate of 200 sccm were introduced intothe plasma processing chamber 9 via the plasma processing gas supplyport 7.

Then, the conductance valve 28 provided between the plasma processingchamber and the exhaust means 18 was adjusted to maintain the inside ofthe plasma processing chamber 9 at 2.67 Pa.

Subsequently, a power of 3.0 kW from the microwave power source MW of2.45 GHz was introduced via the endless circular waveguide.

Thus, a plasma was generated in the plasma processing chamber 9. At thistime, the nitrogen gas introduced via the plasma processing gas supplyport 7 was excited and decomposed in the plasma processing chamber 9 toform an active species, which was then transported toward the siliconsubstrate to react with the monosilane gas, thereby forming a siliconnitride film in 1.0 μm thickness on the silicon substrate.

After the film formation, the film formation speed and the film qualitysuch as stress were evaluated. For the stress, the change in the amountof the warpage of the substrate was measured before and after the filmformation using a laser interferometer Zygo (trade name).

The formation speed and uniformity of the silicon nitride film obtainedwas as very large as 530 nm/min±3.5%, and for the film quality, thestress was 1.2×10⁹ dyne/cm² (compression), the leak current was1.2×10⁻¹⁰A/cm², and the dielectric strength was 9 MV/cm, and the filmwas therefore confirmed to have very good quality.

EXAMPLE 21

The microwave plasma processing apparatus with the microwave applicatorshown in FIG. 19 was used to form a silicon oxide film and a siliconnitride film serving as an anti-reflection film for a plastic lens bythe following procedure.

As the article W, a plastic convex lens of a diameter 50 mm was used.After the lens was put on the support means 2, the inside of the plasmaprocessing chamber 9 was evacuated via the exhaust system (18, 28) toreduce the pressure down to 1.33×10⁻⁵ Pa. Nitrogen gas at a flow rate of160 sccm and monosilane gas at a flow rate of 100 sccm were introducedinto the plasma processing chamber 9 via the plasma processing gassupply port 7.

Then, the conductance valve 28 provided between the plasma processingchamber and the exhaust means 18 was adjusted to maintain the inside ofthe plasma processing chamber 9 at 9.33 Pa.

Subsequently, a power of 3.0 kW from the microwave power source MW of2.45 GHz was supplied into the plasma processing chamber 9 through theendless circular waveguide.

Thus, a plasma was generated in the plasma processing chamber 9. At thistime, the nitrogen gas introduced via the plasma processing gas supplyport 7 was excited and decomposed in the plasma processing chamber 9 toform an active species such as nitrogen atoms, which was thentransported toward the lens to react with the monosilane gas, therebyforming a silicon nitride film in a 21 nm thickness on the surface ofthe lens.

Next, oxygen gas at a flow rate of 200 sccm and monosilane gas at a flowrate of 100 sccm were introduced into the plasma processing chamber 9via the plasma processing gas supply port 7.

Then, the conductance valve 28 provided between the plasma processingchamber and the exhaust means 18 was adjusted to maintain the inside ofthe plasma processing chamber 9 at 0.13 Pa. Subsequently, a power of 2.0kW from the microwave power source MW of 2.45 GHz was supplied into theplasma processing chamber 9 through the endless circular waveguide.

Thus, a plasma was generated in the plasma processing chamber 9. At thistime, the oxygen gas introduced via the plasma processing gas supplyport 7 was excited and decomposed in the plasma processing chamber 9 toform an active species such as oxygen atoms, which was then transportedtoward the lens to react with the monosilane gas, thereby forming asilicon oxide film in a 86 nm thickness on the lens. After the filmformation, the film formation speed and the reflection characteristicwere evaluated.

The formation speeds and uniformities of the silicon nitride and siliconoxide films as obtained were as good as 330 nm/min±2.4% and 350nm/min±2.6%, respectively, and the reflectance in the vicinity of 500 nmwas 0.2%, and the film was thus confirmed to have very excellent opticalcharacteristics.

EXAMPLE 22

The microwave plasma processing apparatus with the microwave applicatorshown in FIG. 20 was used to form a silicon oxide film for interlayerinsulation of a semiconductor element by the following procedure.

As the article W was used a P-type single crystal silicon substrate(face orientation <100>; resistivity: 10 Ωcm) having formed on the topportion an Al pattern of line and space of 0.5 μm each.

First, the silicon substrate was put on the substrate support 2. Theplasma processing chamber 9 was then evacuated via the exhaust system(18, 28) to reduce the pressure down to 1.33×10⁻⁵ Pa.

Subsequently, the heater 114 was energized to heat the silicon substrateto 300° C., and the substrate was maintained at this temperature. Oxygengas at a flow rate of 500 sccm and monosilane gas at a flow rate of 200sccm were introduced into the plasma processing chamber 9 via the plasmaprocessing gas supply port 7.

Then, the conductance valve 28 provided between the plasma processingchamber and the exhaust means 18 was adjusted to maintain the inside ofthe plasma processing chamber 9 at 4.0 Pa.

Subsequently, a power of 300 W was applied to the substrate support 2with the high frequency application means 22 of 13.56 MHz, while a powerof 2.0 kW from the microwave power source MW of 2.45 GHz was suppliedinto the plasma processing chamber 9 through the endless circularwaveguide.

Thus, a plasma was generated in the plasma processing chamber 9. Theoxygen gas introduced via the plasma processing gas supply port 7 wasexcited and decomposed in the plasma processing chamber 9 to form anactive species, which was then transported toward the silicon substrateto react with the monosilane gas, thereby forming a silicon oxide filmin a 0.8 μm thickness on the silicon substrate. At this time, ionspecies were accelerated by the RF bias to be incident to the substrateand to polish the film on the pattern, thereby improving the flatness.After the processing, the film formation speed, uniformity, dielectricstrength, and step coverage were evaluated. The step coverage wasevaluated by observing a cross section of the silicon oxide film formedon the Al wire pattern with a scanning electron microscope (SEM) tocheck presence of voids.

The formation speed and uniformity of the silicon oxide film thusobtained was as good as 250 nm/min±2.7%, and the film had a dielectricstrength of 8.5 MV/cm and no voids and was confirmed to have excellentquality.

EXAMPLE 23

The microwave plasma processing apparatus with the microwave applicatorshown in FIG. 20 was used to etch an interlayer SiO₂ film of asemiconductor element by the following procedure.

As the article W was used a P-type single crystal silicon substrate(face orientation <100>; resistivity: 10 Ωcm) having formed on an Alpattern of line and space of 0.18 μm an interlayer SiO₂ film in 1 μmthickness.

First, after the silicon substrate was put on the substrate support 2,the plasma processing chamber 9 was evacuated via the exhaust system(18, 28) to reduce the pressure down to 1.33×10⁻⁵ Pa. C₄F₈ gas at a flowrate of 100 sccm was introduced into the plasma processing chamber 9 viathe plasma processing gas supply port 7.

Then, the conductance valve 28 provided between the plasma processingchamber and the exhaust means 18 was adjusted to maintain the inside ofthe plasma processing chamber 9 at 1.33 Pa.

Subsequently, a power of 300 W was applied to the substrate support 2with the high frequency application means 22 of 13.56 MHz, while a powerof 2.0 kW from the microwave power source MW of 2.45 GHz was suppliedinto the plasma processing chamber 9 through the endless circularwaveguide.

Thus, a plasma was generated in the plasma processing chamber 9. TheC₄F₈ gas introduced via the plasma processing gas supply port 7 wasexcited and decomposed in the plasma processing chamber 9 to form anactive species, which was then transported toward the silicon substrate,where ions accelerated by a self bias etched the interlayer SiO₂ film.

The cooler as the temperature adjusting means 114 prevented thetemperature of the substrate from increasing above 80° C. After theetching, the etch rate, etch selectivity, and etched shape wereevaluated. The etched shape was evaluated by using a scanning electronmicroscope (SEM) to observe a cross section of the etched silicon oxidefilm.

The etch rate and uniformity and the etch selectivity to photoresistwere as good as 560 nm/min±3.2% and 15, respectively, and it wasconfirmed that the etched shape was almost vertical, and that themicroloading effect was small.

EXAMPLE 24

The microwave plasma processing apparatus with the microwave applicatorshown in FIG. 20 was used to etch a polyarylether (PAE) film as a lowdielectric constant insulator for interlayer insulation of asemiconductor element by the following procedure.

As the article W was used a P-type single crystal silicon substrate(face orientation <100>; resistivity: 10 Ωcm) having on a PAE film of0.6 μm in thickness an SiO₂ film hole pattern of 0.18 μm square formedin 0.3 μm thickness as a hard mask.

First, after the silicon substrate was put on the substrate support 2,and a cooler as the temperature adjusting means 114 was used to lowerthe substrate temperature to −10° C., the plasma processing chamber 9was evacuated by the exhaust system (18, 28) to reduce the pressure downto 1.33×10⁻⁵ Pa. N₂ gas at a flow rate of 200 sccm was introduced intothe plasma processing chamber 9 through the processing gas supply port7.

Then, the conductance valve 28 provided between the plasma processingchamber and the exhaust means 18 was adjusted to maintain the inside ofthe plasma processing chamber 9 at a pressure of 1.33 Pa.

Subsequently, a power of 300 W from a high frequency application means22 of 1 MHz was applied to the substrate support 2, while a power of 2.0kW from the microwave power source MW of 2.45 GHz was supplied into theplasma processing chamber 9 via the endless circular waveguide.

Thus, a plasma was generated in the plasma processing chamber 9. The N₂gas introduced through the processing gas supply port 7 was excited anddecomposed in the plasma processing chamber 9 to form an active species,which was then transported toward the silicon substrate, where ionsaccelerated by a self bias etched the PAE film.

After the etching, the etch rate, its uniformity, etch selectivity, andetched shape were evaluated. The etched shape was evaluated by using ascanning electron microscope (SEM) to observe a cross section of theetched PAE film.

The etch rate, its uniformity and the etch selectivity to SiO₂ were asgood as 660 nm/min±3.7% and 10, respectively, and it was confirmed thatthe etched shape was almost vertical, and that the microloading effectwas small.

According to the present invention, since the radiation characteristicsof the microwaves can be controlled more accurately, the controllabilityof the processing in radial and circumferential directions or adirection equivalent thereto of an article can be improved.

1. A plasma processing apparatus comprising a container, a gas supplyport for supplying a processing gas into the container, and a microwaveapplicator for supplying microwaves into the container through adielectric window, the microwave applicator comprising an endlesscircular waveguide having a plurality of slots provided at apredetermined interval in a plane thereof in contact with the dielectricwindow, wherein the centers of the slots are on a circle having a radiusr_(c) approximately represented byr _(c) =n ₁λ_(s)/{2 tan(π/(2n _(g)))}{1+cos(π/n _(g))} wherein n, is thenumber of antinodes of surface standing waves generated between theslots, λ_(s) is the wavelength of surface waves, n_(g) is the ratio ofthe circumferential length l_(g) of the circular waveguide to the guidewavelength λ_(g).
 2. The plasma processing apparatus according to claim1, wherein the value of n_(g) is within the range of 2 to
 5. 3. Theplasma processing apparatus according to claim 1, wherein the angularspacing of the slots is represented by π/n_(g).
 4. The plasma processingapparatus according to claim 1, wherein the number n₁ of antinodes ofsurface standing waves generated between the slots is any one of 3, 5 or7.
 5. The plasma processing apparatus according to claim 1, wherein thedielectric window comprises aluminium nitride as a main component.
 6. Aplasma processing method comprising the steps of placing an article in acontainer with a microwave transmissive dielectric window; evacuatingthe container, introducing a processing gas into the container; andsupplying microwaves into the container through an endless circularwaveguide having a plurality of slots provided by perforation at apredetermined interval in a plane thereof in contact with the dielectricwindow and configured such that the centers of the slots are on a circlehaving a radius r_(c) approximately represented byr _(c) =n ₁λ_(s)/{2 tan(π/(2n _(g)))}{1+cos(π/n _(g))} wherein n₁ is thenumber of antinodes of surface standing waves generated between theslots, λ_(s) is the wavelength of surface waves, n_(g) is the ratio ofthe circumferential length l_(g) of the circular waveguide to the guidewavelength λ_(g), thereby generating a plasma in the container.
 7. Theplasma processing method according to claim 6, which effects filmformation on the article by the chemical vapor deposition.
 8. The plasmaprocessing method according to claim 6, which effects etching of thearticle.
 9. The plasma processing method according to claim 6, whicheffects ashing of the article.
 10. The plasma processing methodaccording to claim 6, which effects doping of the article.
 11. A plasmaprocessing apparatus comprising an internally evacuatable container anda gas supply port for supplying a processing gas into the container, forplasma processing an article arranged in the container, furthercomprising means for supplying a microwave energy for generating aplasma of the gas in the container, the means comprising an endlesscircular waveguide having a plurality of slots provided at apredetermined interval in a plane on the dielectric window side thereof,wherein the centers of the plurality of slots are offset in a directionparallel to the plane with respect to the center of the circularwaveguide such that the centers of the slots are on a circle having aradius r_(c) approximately represented byr _(c) =n ₁λ_(s)/{2 tan(π/(2n _(g)))}{1+cos(π/n _(g))} wherein n₁ is thenumber of antinodes of surface standing waves generated between theslots, λ_(s) is the wavelength of surface waves, n_(g) is the ratio ofthe circumferential length l_(g) of the circular waveguide to the guidewavelength λ_(g).
 12. The plasma processing apparatus according to claim11, wherein the value of n_(g) is within the range of 2 to
 5. 13. Theplasma processing apparatus according to claim 11, wherein the angularspacing of the slots is represented by π/n_(g).
 14. The plasmaprocessing apparatus according to claim 11, wherein the number n₁ ofantinodes of surface standing waves generated between the slots is anyone of 3, 5 or
 7. 15. The plasma processing apparatus according to claim11, wherein the dielectric window comprises aluminium nitride as a maincomponent.
 16. A plasma processing method of plasma processing anarticle, comprising using the plasma processing apparatus as set forthin claim 11 to plasma process the article.
 17. The plasma processingmethod according to claim 16, which is at least one of ashing, etching,cleaning, CVD, plasma polymerization, doping, oxidation and nitridation.18. The plasma processing method according to claim 16, comprisingashing a 200 mm wafer with the circumferential length of the circularwaveguide being 3 times the guide wavelength of microwaves.
 19. Theplasma processing apparatus according to claim 11, wherein the gassupply port is provided in a side wall of the container.
 20. The plasmaprocessing apparatus according to claim 11, wherein the gas supply portis provided nearer to the plane provided with the plurality of slotsthan to the article.
 21. The plasma processing apparatus according toclaim 11, wherein the processing gas is emitted from the gas supply portto the plane provided with the plurality of slots.
 22. The plasmaprocessing apparatus according to claim 11, wherein the container isprovided with an exhaust pump that reduces the pressure inside thecontainer to 1.34×10³ Pa or less.
 23. A method of producing a structure,comprising the step of using the plasma processing apparatus as setforth in claim 11 to plasma process the article.